[lloeki]

Could also be something like that:

https://scarybeastsecurity.blogspot.com/2020/12/the-cleveres...

I remember reading some article I can't find again about a very unusual floppy protection that involved nonstandard floppy format, something like non standard sector sizes that could be read by the hardware but not written, and the protected software implemented some direct access to the floppy hardware to read data.