I've installed my new modules, ( now I have 8*16GB + 8*32GB), and everything is working OK.
I've also contacted Dell via online support chat (twice) before the purchase - but they tend to just open those first page in the manual and say "no" at first. Next, you say "look here, there's another one" and they change their opinion. But they do not admit those first page is a bit misleading and need to be adjusted. Nice support