I havent denied that, Im however saying that powerlevel wise I dont think Rocks peaked 56 years ago. Surely you agree with me on this.
I think he might be the first god tier in the series.
We have virtually no idea how strong his true ceiling was. We can conclude that Xebec > current and mid gen Yonko based on the fact that he actually killed an admiral and it made him so famous, several top tiers were following Xebec due to his overwhelming power.
At the end, we don't even know if it was Roger + Garp vs Xebec or Roger, Garp, Whitebeard and Garling vs Xebec or if even Imu was involved in killing Xebec. As a matter of facts, Xebec was truly the strongest pirate back then. Not some made up bullshit like Kaido's "1vs1 always bet on him" reputation. Yeah, yeah - Kaido is strong for a top tier but that's it. Xebec shows how a real "strongest pirate" looks like by giving
an Admiral's head for Xebec's introduction.