Jinbe still joins since he's very familiar with the crew as a whole. He's known Luffy since before the timeskip, he fought alongside all the straw hats during the battle at fishman island and was in the big spread with them.
And then at WCI he further interacted with the group. As previously mentioned, recently when someone's about to join the crew, Oda tends to have them develop a more significant relationship with 1 or 2 existing members in particular other than Luffy.
Chopper had Nami and Sanji
Robin is an obvious exception with narrative reasoning
Franky had Robin and Usopp
Brook had Zoro and Franky
Jinbe had Nami and Sanji
They don't have to have a specific interaction with each and every single member of the crew, but they need to be known and associated with enough of them that their integration into the family would feel natural. There's heaven and earth between how the crew knows Jinbe (even before he joined) and how the crew knows...or rather *doesn't know Yamao.