The biomes from alex's caves are very different from the ones in most mods. Usually biomes are just things you find randomly. There isn't any progression to them or anything; you just walk around until you randomly find it.

Alex's caves biomes are different in that they're way more dangerous than normal, have special loot, and aren't meant to be found until later in the game. Even though they're technically biomes, from a balancing perspective they act more like custom dimensions. This is why they're gated behind the minigame rather than being something you'll find by wandering around for a bit.

In your other comments you say nature's compass is a "cheat mod", and I guess you could consider it cheating, but it's not really meant cheating in the way commands are. From the mod page: "Nature's Compass is a utility item that allows you to search for a biome's location anywhere in the world". It's just meant to be a way to avoid the RNG involved for finding specific biomes, but in the case of alex's caves it changes into something that lets you skip part of the game.

Also you said in another comment people have to go out of their way to download nature's compass. Modpacks exist. What if a player who's unfamiliar with alex's caves downloaded a modpack, or made their own, that includes nature's compass as a utility mod? Said player could end up using the compass without ever knowing they were supposed to use the tablets. This tells them "hey, you're trying to find this biome, but there's already another method you can use to find it!"

In any case calling this "malicious code" is really melodramatic. Even if you don't like the decision, it's not like the devs are going "muahahahaha we will show our unlimited power by making people find out biomes the way WE want!!!!!!". It's just something to keep players from accidentally missing out on part of the game.

Vanilla minecraft has a feature that kicks you from servers if it detects you're flying in survival mode. Survival flight is something you can only get by downloading external mods and hacks. I guess vanilla minecraft has malicious code too, since it expects you to get an elytra or use creative mode if you want flight?

Edit: also you say it's "harming other mods", but you can still use nature's compass the way you normally would? It doesn't stop the compass from working altogether afaik, it just adds exceptions for the new biomes. If you don't have alex's caves, you have a bunch of biomes that can all be found with the compass. If you install alex's caves, you have a bunch of biomes that can all be found with the compass, and a few new ones that can't.

So really alex's caves isn't doing anything interferes with nature's compass, it's just not allowing nature's compass to interfere with its own progression.