I understand your logic even though I don't fully agree with it, although this particular bit is kind of frustrating to hear so often. I do agree that, if you're anticipating or hyping up Chun-Li based on this alone - which I definitely have seen people do - then it's misguided. But this is a bit different.
With Min Min and Steve, for the most part, people weren't predicting anything that was very far out of what we could have already reasonably been talking about. A new Pokemon and Rex, for example, were already characters on people's radar. Fortnite had usually come up jokingly before Steve, but was hardly out of the question. These assumptions were founded in the confines of what we already deemed possible - outside of Min Min confirming that spirits can be promoted, which is something that I believe many of us were speculating as is. It moreso just skewed speculation in those directions within the bubble rather than expanding the bubble.
Sephiroth, contrary to these two, breaks down a significant barrier that restricted speculation before. If you had thrown in someone like Eggman or Chun-Li before, you probably would have been told it's silly to expect extra content for third parties when there are new series that can be tackled - that Sakurai emphasized how excited he was to add "new worlds" to Smash. Now we know that it simply isn't an obstacle anymore - and moreso than expecting it, I think most people are just excited that this has been opened up for us. It's a reminder not to limit yourself to these barriers that we've put up as a community and consider that maybe certain standards or quotas matter more to us than they do the guys in charge. It's also a reminder to start thinking about characters rather than just thinking about reps.
I had been supporting Chun-Li beforehand, but I've become much more vocal now after learning that my wishes were not unfounded and actually had a chance of coming true. And with Sephiroth here, there's at least the basis to say that Chun-Li's chances are not that bad. She's one of the most iconic video game characters currently absent from the roster - that alone could justify her quite easily. So I'm personally glad that we're having conversations about her, and validity of that 5ch leak aside I think she's a character people should have been talking about a lot sooner.