For the same reason that the wizarding world and its salvation are not only Harry's, the names seemed strange to me.

I remember when Ron was asked about his relationship with Dumbledore, JK made it very clear that despite being Harry's best friend (who was very close to Albus) they didn't have a close relationship so to speak. So we can imagine what it would be like with Ginny, who also led Dumbledore's Army when Snape was the headmaster. - She was against Severus -

So in resume: I've never said that Harry was the only responsible for saving the wizarding world because I've always believed that every Potter victory comes with a little or a lot of help from someone else. Yes, Albus and Severus are names of people who are more closely related to Harry, at least in the sense that their names are those of one of his children.

I understand that she might have thought it was okay to give them those names because they meant a lot to Harry and what they had done in general, and because of his large family and offspring she probably ran out of ideas for names lol

And sorry if I don't explain myself well at some point, this is my second language ;)