I don't see it in any way different than other SBCs based on the RK3399 - there are countless ones released recently (like the Rock/Pine series). The XU4, despite being 'older' I think it has better support as far as RetroPie is concerned (i.e. emulators tested, graphic drivers, GPIO, etc.).
Do note that a better CPU and better graphics usually mean also you need a cooler/heatsink in these cases.

Yeah, I remember Upton doing a few interviews back in 2017, and he said they were looking at a 2019 release for the Pi 4.
So, like Mitu said, he's either trolling, or they've hit some problems.