I believe this rumor, yet, it's nothing new..... It's what I've been saying all this time. When folk were comparing Vega CU's to Navi CU's, I shook my head, I constantly told them they should not do that. Navi has many more instructions per CU, the whole CU structure was redesigned and beefed up considerably for Navi.
It will take you much less CU's on Navi to get similar performance or more against Vega, and by extension, Pascal and Turing.....It's the same way people are thinking 7nm Vega can be compared to Navi built on 7nm, it's just not how you go about analyzing future technology.