It doesn't matter, honestly. Teach already gained fame as soon as he defeated Ace. He then went on to play a pivotal role in killing WB—and took his fruit—which is what makes him so scary in the first place—and then fought the fleet admiral to a stalemate. That is enough to put him at the top of the world. It didn't take people long to decide he was going to be the next Yonko. The likes of Chinjao and Shanks even acknowledge him as the potential PK candidate.
I don't think he fought sengoku for very long. He also didn't do anything against WB that fodder couldn't do. Yes, he was obviously a major candidate, but its clear that alone wasn't enough to convince people he was emperor.
imo the fact that Teach wasn't initially confirmed as emperor makes it hard for me to see any shichibukai becoming emperor. Like people keep saying buggy's going to do it, but as it stands, buggy has the same amount of territory as Kid. One island.
Nobody has anything more than one island and I don't think anyone got a bunch of territory during the events of wano. Mihawk doesn't want it, neither does weevil, neither does hancock, and buggy is too cowardly to pick fights with the yonko.
I don't think territory is going to determine who's going to be the next emperor. I think its simple, the worst gen captains overthrow the emperors, therefore they will replace them and probably steal their territory. The WG sees this, and makes them emeprors. The only reason you couldn't make the same assumption for teach is, like I said, he was yet to fully prove himself.