I reread the Awsimar description. It is ambiguous. I read the following.
"They resemble their parents", especially their species biology. Except for incidental "hint" of Celestial magic, comparable to cantrip thematics. This subtle magic becomes more prominent as their Celestial magic advances with character level.
Hmmm. On reconsideration, the fact that Awsimar are a "species" means they can only reproduce with other Awsimar and can no longer reproduce with the species of their parents.
In this sense, the "biology" is altered after all. Albeit it isnt actually the biology that changes. It is the planar distortion by the Celestial aster that makes reproduction with other mortals incompatible.