Past fight don't matter over current skill levels. That was made obvious in the rematch. You can't keep holding on to wins from the past and using that as your metric for current match making. The fight to focus on is their rematch because that is the most current and their most current skillset. The Ngannou from the 1st fight is not the same Ngannou in the rematch skill wise.
Stipe is still in the title picture, if Ngannou loses he has an option to skip the line and fight Gane. That's only if he loses, so if Ngannou wins Stipe will have to rack up a win or 2 before trying to get a trilogy fight. You can't exhaust the trilogy option so soon with no fights in between, unless some freak accident happened and there needs to be an instant match to to get a end to fight with no controversy.
Ngannou had to rack up wins before he was granted the rematch, he could've got it way sooner but Stipe wasn't giving him that opportunity until he was forced to. He will get the same treatment from Ngannou that Stipe showed him. Plus there is no interest in the fight currently from the results of the rematch. He needs to build hype by having an impressive win. Not many people think the results will change unless they see something new from Stipe that may change the outcome of the fight. Right now what people are using as a metric is their last fight and Stipe's last performance. If he's currently making improvements he needs to show it.