I think the article is somewhat over-representing the difficulty here. Once you're at the team selection screen and choosing your lineup, there are only 15 possible combinations to choose from. Once you factor in that many/most teams are designed around one or two specific synergies, and that your opponent's team is only partially known (you see their Pokemon species but not the moves, stat distributions, etc), which puts huge error bars around whatever prediction you're trying to make, it usually turns out that you're really only picking from 1-3 realistic choices, and there's a very paper-scissors-rock nature to it that you can't really "learn" in the ML sense.

I think you could have gotten equivalent results on such a predictor using much simpler regressions and/or heuristics, once you've already fixed the matchup.

(Also, I just think it's funny how the paper keeps citing "(Zheng, 2020)", etc, like it's a scholarly article or something. Aaron Zheng is a VGC YouTuber and what is being cited is just an online guide a la GameFAQs)