I think this is it. It's less about "bugs" and more about not, well this. Basically I don't think Apple set up that bus to expect any removable media at all. I guess you could call it a "bug" but really in 1994 do you think anybody predicted camera memory cards would eventually get used as storage replacers for vintage computers?
That said: I do wonder what would've happened if you'd used third party or hacked disk partitioning software. There's an unlocked copy of drive setup hanging around somewhere and tools like Silverlining and HD Toolkit usually work with unofficial storage media. I've been meaning to get an IDE <> CF adapter to play around with and I have a 6200, wo it might be worth looking.
I decided to look at this again since I couldn't recall how I finally figured out that fixed vs. removable was the issue with the CF cards I tried in my Quadra 630. It was not a modern machine via CF USB adapter, my modern Mac running Catalina calls any CF card "Removable". I think this is likely more to do with the USB mass storage driver not caring what the CF card itself identifies as. It was actually FWB Hard Disk Toolkit (v2.0.6) running on an external Orb drive with System 7.5.3 that I was using when trying the various CF cards on the Quadra:
Does not work - "Type = Removable" - SanDisk Ultra II 1GB:
Works - "Type = Hard Disk" - Transcend CF300 Industrial 8GB:
Drive Info for SanDisk Ultra II 1GB:
I/O component type: device
IDE Bus ID: 0
IDE Device: master
Model Name: SanDisk SDCFH-1024
Revision: HDX 3.19
Serial#: 120808G1106A3344
Device Type: Removable
Media: removable
Block size: 512
ATA/CAM compliant: no
Supports Power commands: no
Data rate: > 10Mbs
#Cylinders: 1986
#Heads: 16
#Sectors/track: 63
Buffer size: 1024
#ECC bytes on R/W Long: 4
#Sectors R/W Multiple: 4
Logical Block Address: yes
Direct Memory Access: yes
PIO Mode (word 51): 2
DMA Mode (word 52): 0
Supports PIO Mode 3: yes
Supports PIO Mode 4: yes
Current CHS config valid: yes
Current #cylinders: 1986
Current #heads: 16
Current sector/track: 63
Current capacity(sector): 2001888
Current R/W Mult. valid: yes
Current R/W Mult confg: 4
#Total sectors(LBA): 2001888
------------------------ ------
I/O component type: bus or channel
IDE bus ID: 0
Vendor: Apple Computer, Inc.
Drive Info for Transcend CF300 Industrial 8GB:
I/O component type: device
IDE Bus ID: 0
IDE Device: master
Model Name: TS8GCF300
Revision: 20110407
Serial#: A461909F31120F000122
Device Type: Hard Disk
Media: fixed
Block size: 512
ATA/CAM compliant: no
Supports Power commands: no
Data rate: > 10Mbs
#Cylinders: 15796
#Heads: 16
#Sectors/track: 63
Buffer size: 1024
#ECC bytes on R/W Long: 4
#Sectors R/W Multiple: 1
Logical Block Address: yes
Direct Memory Access: yes
PIO Mode (word 51): 2
DMA Mode (word 52): 0
Supports PIO Mode 3: yes
Supports PIO Mode 4: yes
Current CHS config valid: yes
Current #cylinders: 15796
Current #heads: 16
Current sector/track: 63
Current capacity(sector): 15922368
Current R/W Mult. valid: yes
Current R/W Mult confg: 0
#Total sectors(LBA): 15922368
------------------------ ------
I/O component type: bus or channel
IDE bus ID: 0
Vendor: Apple Computer, Inc.
I have two other CF cards of each type (fixed vs. removable) that are of different brands/sizes and confirm this behavior. Apple simply didn't plan for these Macs to work with IDE devices that identified as anything other than fixed hard disks.
Also interesting in the detailed info is the "PIO Mode (word 51): 2" info, even though the card is identified as supporting faster modes 3 and 4. Seems that these early IDE Macs, at least with 7.5.3, supported only up to mode 2 which has a maximum transfer rate of 8.3MB/s, although that's notably/theoretically faster than the SCSI 5MB/s maximum of all but the high end Power Macs of the day.