You’ve nailed it. Customisation is just overhead for a volume builder so they’ve started charging for the luxury of it. Although, I think there are some elements of expertise they’ve added to the process which isn’t so bad.
They have always charged for it. Maybe not as a line item, but be sure they didn’t do it for free.
And one would hope they now provide some expertise. One of the things I am most u happy about with my place is a variation we made to the kitchen, based on their advice. But once we signed on the dotted line it all became too hard for them and I had to come up with a way to make our kitchen work. I couldn’t even talk to their kitchen people to get a kitchen design that would work.