It might've been an idea Oda had but at the end of the day, it's a fan theory shown in a SBS over a decade ago. The fact that it was shown in the SBS period should put people off from it. Why would he show his method of determining the last SH a decade ago?
Yamato is factually Oden's successor at this point. The anime has made it abundantly clear for the people not looking at their stories side by side thanks to the numerous parallel shots. I could break it down if you want but it's easy to see how much Yamato and Oden naturally have in common with their stories.
Along with this being a loose criteria that doesn't apply to every member, Zoro was the one to invite Usopp.
Yamato and Jinbe have a lot more connections than he does with Carrot. The simplest comparison being that they both fought and befriended Ace, who told them to look forward to Luffy. I feel like that's something they can bond over as well similar to how Brook and Robin were about their trauma.