Sorry to interrupt--I wasn't going to weigh in on this, but that isn't quite correct. I wouldn't have said anything, and I have no view on what you call your books, but since it's been stated in a 'factual' manner I need to clarify what the A5E terms mean.
Synergy feats don't need to be feat chains. The synergy feats in the AG
also happen to be feat chains, but you can have a single synergy feat with no chain, or a feat chain which does not use synergy feats. Synergy feats were the second name we settled on after we were originally going with 'prestige feats' (like prestige classes, which often required levels in various classes to access). For the record, I prefer the latter!
You, of course, can use the terms differently in your own books, but in A5E the terms are not synonyms.