"League winner". The "League champion" term has never been used before now. That's part of the issue really, they're introducing this "new" term that's mostly just an old term apparently repurposed.
No, see, there's the issue: They've never said anything about the champion of the Alola League becoming the Champion of the Alola region. And that's the problem with this entire "league champion" thing - they just toss the term around and never really explain what it's supposed to mean, and half the time they just shorten it to "champion" too.
Wait what does the anime refer to the Elite Four and Champion, because technically the Pokemon league is the Elite Four Championship in the games. So what did the anime refer to it as differently.
While the tournaments are referred to as conferences (at least in the English Dub), because the conference is the FIRST step of the Pokemon league (after getting badges of course)
In the anime the Pokemon league encompasses they gyms battles, the conference tournament where the winner of THAT would challenge the Elite Four and Champion, it's under the same umbrella of "League"
I'm not entirely sure why you aren't considering that the Alola League Champion is the SAME exact thing as an Alola Region Champion. When every other generation the characters were the SAME exact thing.
Sure, maybe not in Japanese, maybe there are some nuances in the way the Japanese described the Elite Four and Champion that doesn't relate to "LEAGUE" but I don't know that makes sense, when the Champion of a region is the final challenge for a Pokemon league.
They're not two entirely different things since in the games, they've primarily been solely ABOUT getting gym badges, battling the Elite four and the Champion. The anime just adds another step to that process.
Because there's NEVER been a champion in ANY media that I can think of where the Champion of a region was different than the technical Champion of a regional's league. To clarify I mean a champion of a region that's UNrelated to gym badges, and or the Elite Four, because Alola doesn't HAVE gym badges, but it does have an Elite Four. Like Cynthia being the champion of Sinnoh isn't different than Cynthia being the champion of the Sinnoh League since you have to look at it from how its presented. Cynthia is the final challenge to overcome, both in games and in the anime, for the SINNOH region. How could the champion of a league or a champion of a region be any different when LOGICALLY as its been presented they are one in the same as being the top challenge for the regional "league/challenge"
Unless you really think the Alola League Champion ONLY applies to the conference tournament, which sure, fine, I guess that makes sense. A tournament should end with the title of "Champion" because "Conference Winner" doesn't seem to hold that esteem.
HOWEVER as I should point out YET again. Why wouldn't the winner of this Manalo Conference not be referred to as the champion of the Alola region? As I said repeatedly, in the anime, there's no where to go from here. Other regions had an elite four, and Champion to take on. Again there is NOTHING here in ALOLA like that. So how could Ash or Gladion not be THE top trainer of the Alola region which in other regions it's been the Champion.
At the moment the winner of this conference has plateau'd at the top. It doesn't get any higher than this. There is no other challenger. Especially with Masked Royal being an Exhibition Match and all which I believe means "Unofficial."
But whatever, I don't know the intentions of the writers, I can only guess based on what has been presented to what is being presented.