I know that at least in Sun/Moon, sometimes NPC guests give more FC for correctly interacting with them than usually, which is after the fortune teller says you'll have decent/good/pretty good luck (increasingly higher rewards) in Festival Plaza. So it's nothing to worry about. IIRC nothing really changed in the Ultra games (US/UM use the same engine as S/M (so technically US/UM are ROM hacks of S/M - a wonder Nintendo approved /j)) when it comes to Festival Plaza except they added a new facility and of course the
shenanigans.