They are not the final character of the biggest fighting game of all time, CP11 is.
I mean, yeah? But that doesn't mean the last character is going to be treated differently. Not saying it can't be the case. But we don't know for sure, and when things are uncertain, I prefer to stick to the logic dictated by past events. And that tells me that the last fighter is probably set to be revealed during the Nintendo Direct we're expecting for this month.
Still, I won't deny there's an option they might go with a Sakurai Presents for the reveal of the final character. That would mean the Nintendo Direct would give us the date for said Sakurai Presents. But they're not going to say "hey! We're not announcing the character today, sorry. If you wanna find out, tune in for a Sakurai Presents scheduled for... the end of October".
If the reveal for CP11 is kept until a Sakurai Presents, we're not really going to wait much more for that after the Nintendo Direct, Like, imagine the Direct takes place Wednesday 15th of this month and they announce a Sakurai Presents for the last fighter. I'm pretty sure if that happens, the Sakurai Presents would be scheduled not that many days after the Nintendo Direct.
So in the end I don't see that much of a difference. We're still getting a Sakurai Presents regardless of where they announce the character though, so if you're implying CP11 would be revealed there and not during a Nintendo Direct, and the reasoning for that is that "this is the biggest fighting game of all time", I fail to see the logic.
In fact, if CP11 was indeed Nahobino the best way to announce him would be during a Nintendo Direct. Because I'd assume boosting SMTV potential sales and all of that would be a significant part of his inclusion. Sakurai's presentations get a lot of views, that is true, but Nintendo Directs even more for obvious reasons.