IIRC according to him it was something like BB getting WB's DF and maybe Whitebeard/Blackbeard naming.
To be fair, there is certainly some portrayal that BB/WB shares. But characters can share portrayals without being parallels. "Joyboy" Luffy/Ryuma share portrayals, but Luffy's ancient parallel is Joyboy and not Ryuma (who is Zoro's ancient parallel).
It's very obvious Blackbeard is Rocks' parallel, he is acting as Shanks' nemesis/antagonistic rival, similar to Rocks being Roger's antagonistic rival. While Mihawk is the friendly rival of Shanks, who has a world's strongest title, that share drinks together, like WB being Roger's friendly rival.