ST, Amiga and PC all used the same magnetic encoding, called MFM[0], so differences were completely logical (and not even very different - e.g., the ST and PC both used the old CP/M "FAT" format that is still with us today). That was more like having a file that's at the same time a .c program and a shell script. Nice, but at a rather high level of abstraction.
Apple II and the C64 used GCR[1] encodings (not the same GCR encoding), which is completely different. A C64 drive controller cannot read MFM, and a PC disk controller cannot read GCR.
The interesting thing about this hybrid disk is that whoever made it alternated the tracks - odd were GCR, even were MFM, and the logical filesystems were arranged such that each file system respected the other filesystem's tracks.
[0] https://en.wikipedia.org/wiki/Modified_Frequency_Modulation