By adding the a SCSI controller, it's possible the weighted score may change enough to require reactivation. If the drive is in the same machine already, it's possible it might work. In the end, while an annoyance, reactivation is fairly simple.
IMHO the SCSI drive must push more than the ATA100, and if it's only UW, I don't see that happening. Does it have a better seek time?
DC