I don't think it's this.
I'm almost certain that he got a lot of 4★ girls, but rather than combining and evolving them, he instead kept them as duplicate/triplicate/multiples, and got rid of his 3★ to preserve inventory space. And by all accounts, he must also be dealing with the default inventory slot, spending all flowers on pulls, instead.
This means even if he were to combine out his 4★ girls, he'll end up with less girls available, and even be a team or two less. I'm assuming he's still an early player, less than a total of a month under his belt.
I kept 3★ girls even after 2 months, because they were still powerful, with 100% affection and evolved, than a fully leveled 4★ girl. Eventually, with more events, lucky seed gacha pulls, and careful flower management/spending, I had way too many 4★ and 5★ girls to make 4 teams with, and replaced my 3★ girls when I capped affection for the higher level girls. The process probably took 4 months or so in total; other players who had more time to play this game probably could do it in half the time. Unless you're a whale, in which case you could probably do it in one day.
(edit: I'm an F2P player, and don't spend a dime on browser games)