I would make the argument the Power Macintosh G3 itself also stood in as a reasonable "consumer" machine - despite not being available in a Performa bundle (which, really, the Power Macintosh 6500 was in everything except name.) Especially in early 1998 once the 6500 was killed and Apple had dropped the base price of the desktop system to $1299, making it a pretty reasonable "slot in where your old Mac sat and install your old stuff" upgrade to almost any older system, or pretty basic office system.
The 6500 itself sold for a few more months after the launch of the Power Macintosh G3, but Apple had known for years that consumers didn't really want another rehash of a rehash-rehash, and even if you drop a G3 CPU onto a 6500's board, or even if you design a G3 motherboard for that enclosure -- everyone can smell the 1993 from a mile away. (This is directly stated, more or less, in Apple's annual reports dating as far back as 1996.)
Whether or not Apple
condoned opening the iMac G3 - it was widely done.
So, yeah, technically there were a few months where Apple wasn't building a consumer machine. Although, you were around back then. 6500, 6400, 4400, 6360, and even regular 6300 and 6200 variants were still on sale in spades. (*Another problem Apple acknowledged openly in its annual reports.) So if you wanted a performa bundle for those few months, it wasn't hard to get it, although why you would, given how early in the year Apple teased the iMac G3, I don't know.
I don't often refer to Macs by their architecture name or codename, I often find it more confusing than just saying the well-known model names, or in some cases well known identifiers (esp. Power Macintosh G4s). So, every single time I see Alchemy and Gazelle, I have to search online to recall what those are, but I already know what's involved in a 6400 or 6500 and I remember most of the stock specs of most of the variations off hand for those two models in particular too. (At least at the moment, much of that's been via digging through old MacWorlds.)
In most iMac G3s, the CRT is sufficiently far enough away from the other meaningfully important parts that you can work in them without fear of getting zapped, although in the slot-loaders, there are a few pesky places screws can get to. Those systems changed the system up a little bit so the RAM and AirPort slots are available directly under a hatch you can open with a coin or the blunt end of a house key. (However, getting to PRAM/ODD/HDD requires a few more screws to be taken out.) I had an original iMac G3 and pulled it apart a little after I got it, IDK, probably when I was eleven or twelve, to put some more RAM in it, and didn't have any real trouble. It was annoying but it wasn't impossible or unsafe.
And, yeah, the Beige G3 AIO board is almost identical to the minitower/desktop boards. I don't think it slid into a cable harness, there was a big nest inside, but I haven't personally had one and it's been a few years since I gandered inside one.
Regarding the timeline:
1997: Gossamer is the beige G3 motherboard.
1998: The Beige G3 is speedbumped, still on the Gossamer board.
1998: The iMac was released in 1998, not 1999.
1999: The iMac was speed-bumped and released in colors, the Beige G3 was replaced by the blue-and-white "Yosemite" G3.
I saw a mention of buggy -- I couldn't speak that much to whether the 6500 is buggy, but I had a 6500/250 for a while and it didn't seem that bad? That was around fifteen years ago at this point, however. Was it that the 6360/6400 were buggy and the 6500 fixed that? Or, does "bugs" mean something else here?
Regarding the slots in the G3 AIO: - Schools were used to the 4/5/6 series Macs, most of which didn't have all that much expansion. I'd put money the only reason the G3 AIO exists the way it did was because Apple wanted to have their product line and supply chain be as simple as possible. Tim Cook joined Apple in 1998 and his background was in logistics and supply chain management. I'd be zero surprised if it was at his insistence Apple would build only one motherboard for all three G3 machines, and also that the iMac G3 and PowerBook G3 would be electrically so similar. (And, the Walstreet is basically a miniaturized beige G3, platform-wise.) Apple was headed that direction anyway, however.
Something closer in shape to the iMac or eMac is what education has always wanted - something short, so kids can see over it. If you've ever been in a K-12 school computer lab, you know visibility is a big issue, and many of them are both task/work spaces and instructional spaces.
In Education, the only people who ever installed cards in years-old Macs as a way to retain or add value has been people who had a home page and were extremely passionate about computers from the outset. I'm going to hazard a guess that there were fewer than 50 total such educators who were so technically inclined as to be doing things like
rebuilding machines on their own.
Strictly speaking, I'm not sure the 6000 or 5000 series was ever what educators really wanted, either. It just happens to be that Ethernet cards were easy to add and those systems were flexible in that they could be used for general purpose stuff or multimedia without breaking the bank, relative to having to buy a bunch of 4400s or 7200s as inexpensive general purpose lab machines, and then a few really expensive 8500s for audio/video work, presuming there's ever been a really compelling use case for that specifically, outside of multimedia production classes specifically. (i.e. asking a room full of students to make a video book report has probably never gone well.)
.. Anyway. A lot of that really has to do with the fact that education has relatively unique physical needs that happen to often match up okay with what consumers need, but they're pretty unique markets, still.
I'd guess many load up their TAM HDs with lots MP3s to take advantage of the sound.
