Ok level caps are fine that's a thing in normal pokemon games but what I'm not ok with is people somehow doing gyms with -10 levels...seriously just what the hell are they doing to get away with that? I can do -5 to maybe -7 but 10? what's the secret?
Base stats.
The stats of the waifumon are boosted to make them more interesting to use with their improved learnset.
Now mind you. The dev team are not arguing that leveling to the same level as the gym leaders ace, or overleveling, is a bad way to play.
Pokemon H was always intended to be more focused on the gameplay instead of the porn. The dev want to give a fun, challenging game where the porn is second and considered a bonus.
There are multiple ways to make the game challenging. Trainers mons are strong and troughout the game they are more and more handcrafted to make sure to give you a hard time.
The level scaling has also increased. This is not so much an issue in the early game, but later on you will notice you fall behind a bit in levels.
Now, aside from the game being challenging, its also important that the game is fun. If you struggle all the time to keep up, the game becomes a slug. This is not appealing to the majority of the fanbase, understandibly.
Therefore the waifumon have increased stats. Some reaching legendary pokemon base stat totals. This way you will have strong pokemon who can keep up with pokemon that are higher levels since their stats are carrying them.
This way the game can give you fun and OP pokemon with the enemy having higher levels being one of the ways to balance the game.
As for the reason the level cap is introduced. It was simply voted for on the patreon... The question was raised if there should be a level cap that is not optional. The poll was passed with a majority.
This way we will put another challenge on the player. But certainly not one that we deem impossible.
This is also in the spirit of the game, how Sintax wants the game to be.
A challenging game with a fun story, with porn.
As for the -10. yeah we have a BETA tester who is more knowledgable about competative pokemon who beat Gym for while, on average, being 10 lvls below the mons of the gym leader. I can do it with -5 to -7 but it does take some retries and readjusting pokemon positions wich is a fun puzzle to me.
Hope I answered your question and gave a bit more insight in the thought process.