I cancelled the Sync, it stayed stuck & spinning, so I "ejected" the iPhone 6S.
Somehow most of the restore was on the 6S, but I had to install 9.0.1 and update some Apple apps that had already been updated on the backup I had, so color me confused.
I updated the software, updated the apps, restored some purchases that weren't on the phone, then compared 6 & 6S purchased apps and readded other purchased apps that were on the 6 but not on the 6S.
Strange. Almost like it restored parts of an earlier backup, but things like texts are up to the minute up to date.
I don't know if this is going to be some kind of corrupted image or not? Guess I'll wait and see.
Will keep the trade-in 6 the full 10 days before returning it just so I can access the old image if needed.