Tbh Oda retcons shit all the time for the sake of plot and narrative
You'd think the pirate king would defeat somebody well-known or strong like even mid-tier famous pirates like Captain John or Ganzui or even Chinjao
Instead his biggest W was Squardo pirates and the most famous stories out on sea are about almost getting caught by "hero" Garp
Xebec instead got everything Roger couldve had strength-wise