Regardless of who pays faster, it’s playing on two fronts, one which attracts a lot less attention than Steam. They get to reduce the price to a point where it might get a rush of sales (we don’t know the revenue split), without having to compromise too much on the Steam front.
Realistically, they’d have to wait much longer than a month to cut the price to an equivalent level on Steam, without getting hell for it, so even if IndieGala pays slower it’s still a shorter wait.
Usually this justification goes, we didn’t read the fine print / they made us do it.
Thanks for the nice words, the other option seems more likely, though.
There you go.