I think you're forgetting something.
Alain defeating Korrina as his LAST badge, not the third badge, I don't think it matters that Ash battled her as his third. And not to mention I think Barry beat Bryon before he even beat Fantina and was actually struggling against her, whereas Ash battled Fantina before Byron, and I'm sure Byron was the more difficult opponent.
Korrina naturally would have to be a lot stronger by now anyway, since she just barely got used to Mega Evolved Lucario when she challenged Ash, and true Alain was whole beast and half but he still battled her last.
So yes I can easily see her being stronger than Ramos (who doesn't have a mega evolution), Valerie (because Lucario is part steel), Clemont/Clembot (because I doubt Clembot would be stronger than Korrina), I can see her being stronger than Olympia (at least on on one, with Mega evolution Lucario vs one of her Meowstic, double battle wise Olympia might be stronger if Maylene doesn't have at least something to combat Olympia in double battles, but I imagine a Pangoro for example would be very helpful).
Lastly is Wulfric, which even if we assume was the strongest trainer, keep in mind Mega Abomasnow for the most part should've been more powerful than Ash-Greninja, let's face it, Mega Lucario just completely destroys Abomasnow, so yes I can technically see after all this time, Korrina is technically the strongest gym leader.
Again I'm not saying she needs to be rank 10-99 which is where the Elite Four should be ranked I was never saying that, but I could easily see her being around 700-800 easily. Keep in mind there are about 900 trainers in this next rank, if we even include the Galar region that's 7 generations of gyms (Alola didn't have any), that's about only ~56 trainers, so they could easily be 300-400 or something if need be. And let's even take the Elite Four power level rank which should be below Master rank, that's about 100 trainers still (though maybe less but close to 100, 90 I think), even including ALL the regions that have Elite Four members that's only 6 generations of Elite Four (8th generation doesn't have Elite Four members, and unfortunately anime wise neither does Alola region) that's only 24 trainers out of 100 possible trainers.
I think people don't understand. All the gym leaders could easily be the "Great Ball rank" and still have PLENTY of other options. All the Elite Four can even be in the Ultra Ball Rank and still have plenty of spaces left over, whether they do that or not is an entirely different question. And technically the master class could technically fit all the champions.
Kanto and Johto- Lance (1)
Hoenn- Steven (2)
Sinnoh- Cynthia (3)
Unova- Alder (4)
Kalos- Diantha (5)
Alola- Ash (6)
Galar- Leon (7)
Galar- Raihan (8)
Replacement for Ash before Ash joins the Master Class- Who knows?
Yes technically not all the champions will likely be in the master class rank, yes not all Elite Four members will be in the "Ultra Ball" rank and not all the Gym Leaders will be in the "Great Ball" rank, some could be higher some could even be lower (not necessarily the class but at least rank wise prior to master class). Like the strongest gym leader could technically be the first opponent or first challenge in the Ultra Ball rank, it could be feasible. But aside from that it's still entirely possible.
So Korrina could easily be around rank 200-600 if they really wanted to. I'm just saying she shouldn't be in the 99-9 rank (the Ultra Ball Rank) as that should be purely Elite Four level strength. Like I would believe a frontier brain would be in the Ultra Ball rank far more than a gym leader.
So no, Korrina could be at rank 500 for example, and was kind of more what I was hoping. I don't want her to be rank 999 and Ash being at rank 1000, it's why I don't want Korrina this early in a PWC match, because I do believe Korrina could be higher than 999. And I kind of wanted a more random entry into the "Great Ball" Rank that could be its own episode. I just don't like that Korrina feels like the last Normal Class trainer for Ash, when she technically should be stronger. Like I said the gym leaders should easily fit just fine in the "great ball" rank, which is what I would've preferred. I don't want gym leaders to be in the Normal Class where up to 10,000 trainers can participate, that's not going to make for a naturally good battle because you're being paired with gym leader substitutes and random nobodies (at the moment), at a class where everyone can participate in, you see the problem there? Gym leader should be in a higher class than that, I think it makes sense. Again some people just won't make it, primarily due to the character traits and the writing. Fantina probably doesn't care about PWCs.
But I mean strength wise, people in the Great Ball rank should be gym leaders at their full strength, the "Ultra Ball" rank should be Elite Four level trainers at their full strength, where Master Class will be regional champion level trainers at their full strength. But whether that happens, remains to be seen.
Only by pure strength wise of mega evolution, because it's not like adaptability will help bone rush at all, which otherwise would just be a normal non-stabbed move.
Lucario's hypothetical steel type moves would be far more effective than bone rush, since adapability is like dealing super effective damage on an opponent but without stab, so a steel type move definitely should be more effective given its higher base power. But it depends on whether they want Bone Rush to have a crazy high base power (anime only) or the steel move.