Well well well, in the most obvious example of Occam's razor since Brook joined, we have someone who said nearly 70 chapters ago that they would join the crew finally join the crew. There was room for doubt in 985 when Yamato was just introduced, but then 1016 happened and there was no reason to doubt. Now we got Yamato saying it to the crew. There ain't no walking back from this one. This is what we call an inherited will, people. A dream. A desire.
B-but Jinbei said!
Jinbei is always the straightman to the absurdity of the rest of the crew. Remember how Jinbei reacted to Drake wanting to join the alliance. Luffy immediately accepted for a Jinbei gag. It's going to be the same thing here.