With current advances in magnetic storage technology, I don’t think it strange to produce a disk that small, holding the same amount of data as the original 5.25” disk of its day...
The real challenge: Making a disk drive, and controller to match. (Not sure which way to go there: Is that even possible?)
The 5.25 Disk ][ (and subsequent smartport and other DB-connector models) were single-sided 35 track drives, with 4k per track (140K, sometimes metricized and marketed as 143K, a stupid fictional number). The 32GB thumb drives and flash memory cards widely used today have over 1000 times more storage than the ProDOS hard drive volume size limit, and 32megs was more than adequate for an OS that would boot off a floppy.
Those were the days...
;’)