of course it controls the head position regardless of the physical platter, so it wouldn't really be helpful unless the drive only had a single platter in it. i've never seen an actual chip soldered in here and it was completely removed in later board revisions, so i guess they never fully implemented it.
@tubetime you got impressive knowledge from analysing these drives. It's unheard of. This will be so useful for anyone wanting to fix these drives, thank you so much for the full #retrocomputing community.