"Alolan Champion" has been used before by someone credible:
SM115
ライチ: 「それわまさにアローラのチャンピオンを決めるバトルだと思います」
Indeed, but
she wasn't talking about the league there, but about those long-gone battles on Lanakila Mountain. She's not saying the league determines the Champion of the Alola region, but that in the past, Alola used to have battles that did this. They then go on to break down the difference between those battles and the league.
The same episode also had Kukui specifically saying that the League was a tournament "to determine the strongest trainer in Alola; The Champion!"
ﾎﾟｹﾓﾝﾘｰｸﾞは至ってｼﾝﾌﾟﾙ｡ 誰がこのｱﾛｰﾗ地方で いちばん強いのか ﾁｬﾝﾋﾟｵﾝを決める大会です｡
Yep. As I've pointed out earlier, they keep calling the winner "Champion of the Alola League", and often just shortening it to "Champion", both in the show itself, in summaries and in magazines. But they never say "Champion of the Alola Region". That was my point when I broke down the terms they use in that earlier post.
(it's also somewhat amusing that the new TV-kun scan spends most of its time talking about how it's a very real possibility that the strongest Trainer in Alola is Kukui and
not the fresh champion of the league)
EDIT: Also, another thing that came to mind - remember how they've constantly being going on about "the first ever champion in Alolan history" and all that jazz? In SM115 Lychee specifically mentioned that in the past, Alola DID have regional Champions just like all other regions, complete with some vaguely-alluded to battles for determining who the Champion was. Surely that's a pretty good indication that "the first ever Champion of the Alola League" is something different from these Alolan champions that were a thing in the past, otherwise he wouldn't be the first.
