I'd never seen eMMC on modules, but it may also be mislabeled PCIe or mPCI, if it's, say, for a Dell mini9 originally, or it may be an M.2 module that is a bit closer to a "real" SSD. Most systems (I've researched in detail) with eMMC are built using a module on the motherboard, so it's interesting to see it modularized into an m.2/mpcie-like/msata slot. That system instantly becomes more interesting if you can upgrade it to a 128GB module, even if that costs almost as much as the machine itself.
(see also: original iMac, appropriate USB adapters, big external SCSI disks.)
eMMC, like a lot of other technologies, isn't a single thing, either. It (as with regular SSDs) comes in different quality grades and different speed ratings. The Surface 3 I have uses a 128GB eMMC for its boot volume, and it's noticeably slower than a "real" SSD but it's still not "bad" per se.