[dunham]

My fuzzy recollection is that the option board could read the entire track at once, raw - not MFM decoded, where the typical controller in a PC had a high level interface that only gave you sectors.

One copy protection system that I remember was a track that had a mix of long and short sectors with the short sectors embedded in the middle of the longer ones. (Sectors header/footers were marked by special bytes that were illegal MFM coding.) If a program tried to copy the the track with a normal floppy controller, they would have more sectors than would fit on a track.