you alway have to remember that everything they sell will fall into one of three categories. It’s right, it’s wrong but can be made to work and it’s just wrong. The trick is learning what you can trust and what you can’t.
As for panels, I suspect the more complex, or subtle, the shape as well as the size the more work will go into making it fit correctly. Door skins I agree were a lot of work to use and you’d really have to think about it before doing them. On the other hand I used a trunk floor from them several years ago that was pretty good and didn’t require lots of work to fit. Their panels, last time I got any, were from one of the British vendors, although I don’t recall which one offhand.