Ok, replying for Joseph here as he sent me the file for comparison (I believe he wasn’t able to compare 4.0 vs 4.1 in these current moments) - so, I have done so.
It does appear to be identical in 4.0 (current beta) and 4.1; if there are differences, I haven’t been able to see them. So i think Brecht is correct, in that it’s related to the BSDF differences (arg) coming in 4.0.
So visually, it feels somewhat safe. In terms of the node/math situation - still a Node Thank You.
NoDE Thank You. That’s funny, admit it. 