Presumably, NEC's FIRST external USB drive used a general purpose USB floppy controller, but probably by the second one, they made it very specific to 1.4M
Sorry. Thinking about it, It is probably NOT making the controller more specific to some formats; (although updated drivers probably do not support anything but 1.4M)
Instead, it is probably that they made an integrated drive and controller, which unfortunately means that we can't just separate the two parts and substitute a 5.25" drive.
