That's kind of odd because I think 1990 already had mostly IDE drives which really shouldn't need that. The much older MFM and RLL drives might have had more tracking issues and "format", but then also had huge tracks so even that sounds absurd to me.

I do recall that people used to worry about whether mounting drives sideways was going to affect the life of the bearings on the main axle spinning at 5400 RPM or what have you.