Same multiverse =/= same continuity as the games. The games are canon to it, yes, but there's no proof it's also true the other way around.
And no, Masters shouldn't scale because the scalings are incredibly inconsistent with showing from the games. For example, Giovanni's Nidoking overpowering Silver's Ho-oh, Cynthia's Kommo-o defeats Cyrus' Palkia, Misty and Brock are able to fight Barry, who before then already got all eight badges despite them being way weaker in the games, and many more examples
Also, as I said, the fact that Ingo exists in Pokemon Masters contradicts Pokemon Legends Arceus, so it can't be canon to Legends Arceus