From what I know when a drive "reallocates a sector" it actually reallocates a track or something very close to that. So that at least for the rotational sequencing the performance will not change that much. Ofcourse, the track that used to be just one track seek away now became further off.

There are also several places along the way where reallocations go to and the drive tries to find the closest one to the reallocated tracks to avoid too large seeks.