Worstgen
Salah WG
WB wouldn't talk about Shanks/Mihawk Duels when Shanks became Yonko much later & even call them Legendary unless Chapter 1 Shanks was already Yonko Level (WB also said that everyone was Shocked that Shanks lost an Arm, something i don't think People said about Crocodile for example). Shanks/Mihawk when Going All Out are clearly from a Level we haven't seen yet imo (I believe only Dragon is comparable for now)
Monkey D. Luffy
Don't forget Thatch said a Division Leader said scarring Shanks's would've been a big deal.
Seth
Don't we find out that Shanks became a Yonko 6 years ago during the timeskip.