And that’s just headcanon.
What? That Blackbeard used his fruit to stop Boa? That Blackbeard himself said that Boa would turn them to stone if he let go?
BB didn't fight the seraph head on. Just used a single move. He also tanked the seraphs attack too.
As I said, as the warlords strength increases, their difference to their seraph decreases and even surpasses the seraphs. Mihawk is at top. Boa is like 2 or 3. Jinbe is in the middle.
If seraph jinbe can use all of jinbes moves, I will agree that it's better than jumbo.