HP and/or Compaq used to make their own PCs in the 90’s going into the 2000’s.

For example they used to have special motherboards that were basically backplanes and CPU cards to suit.It’s quite possible they did dumb shit with IDE connectors/pinouts that meant that some devices didn’t work.

It wouldn’t have been a major scandal, it just would have been, “yeah some aftermarket drives don’t work with HP”, which was pretty common across the entire market back then. We’re basically in the golden age of system compatibility right now, things were an absolute shitshow back then.