Probably for a lot of them, yes.I see your point but wouldn't that be a problem with any Terraformable world?
The description of the planets on the system map implies:
- high metal content: lifeless
- water world: water-based life
- ammonia world: ammonia-based life
- earth-like world: water-based life and human-breathable atmosphere
So some of the HMCs are going to be terraformable without wiping out the existing life, and its a big galaxy so no need to do the others.