I have been in plenty of FP treasuries with a lot of depth and a mix of backgrounds. I think it's just a matter of the taste of the particular admin who's picking on any given day. If you watch, there will be a whole day of white, white, white and then it will change up.
I don't necessarily think that's a bad thing. I, personally, don't connect with the homogenous white backgrounds, but those with a more modern, minimalist aesthetic probably do.