New Game s1 only adapted two volumes. Even s2, which had no filler material, only adapted three volumes. Going back a further, Kiniro Mosaic's volume 3 didn't even come out until after the is first season had ended. A-channel's volume 2 came out like a month before its anime started.
I can't actually think of any instances where a 4koma anime adaptation used more than three full volumes of material. And even then, given standard production time, if a Swap anime had been announced in place of Anima Yell, Swap would be most the way through the fourth volume by the time anything started airing. Comic Girls' anime was announced a month after its volume 3 came out (coincidentally, the same timing as Blend S's announcement). So the claim that Swap doesn't have enough material yet is just outright incorrect.