Sounds like it could have been a miscommunication between hosts there, seems likely that some people would have been checked twice and others not at all due to one host checking entire rows whilst another does one side of the train. Presumably this means Towers will now have to go down the Legoland route and enforce double checking on every ride with hosts telling everyone they're secure followed by an "all secure" announcement by the op
Whilst I don't know about Galactica specifically, on a lot of rides the restraint monitoring sensors only detects that the restraint has reached the minimum closed position. This may not be suitable for all passengers (i.e. small/thin people) and on some rides may not even guarantee the restraint is locked. That's why you almost always have a physical check by ride hosts - it ensures there isn't an unsafe gap between rider & restraint and that the restraint is actually locked, not just closed.