Do traversal skills replace combat abilities?

This means you can pick your fighting team purely on how it fights. An Aniimo you never field in battle can still be the one that gets you up a cliff face, because the creatures you use for flying, climbing and swimming live in their own menu and do not have to sit in the active team. Equipping a mobility skill takes nothing away from your combat kit.

The practical upshot is that there is no trade to think about when you find a creature with useful movement. You do not have to bench a damage dealer to keep a climber. The two loadouts are decided separately and neither one pushes on the other.

What counts as a traversal ability

Each Aniimo brings its own distinct physical traversal ability while twining, and between them they cover most ways of getting across the map: sprinting, climbing vertical walls, swimming, diving, gliding, flying, and burrowing underground. The traversal menu is where you decide which of those you want on hand.

Aniimo that carry movement skills

Celestice provides level one climbing and flying. Celestis handles climbing and gliding, through the Climb and Glide abilities. Emberpup has Hustle, an active ability that lets you sprint.

Because none of these need a combat slot, a creature whose only real use to you is its movement is still worth keeping.

Not settled: How much room the traversal menu itself has is not settled. Nothing fixes how many mobility skills you can keep equipped at once, so it is not clear whether you will eventually be choosing between climbers and swimmers inside that menu even though you never choose between them and your fighters.