Yoga is not a religion. period. It is a breathing exercise while holding certain positions.It is neutral in “religion”.It can be used by any one who has whatever religion or someone with no religion.
To call it a religion is like saying doing crunches or touching your toes is religion. Or to take slow, deep breathes to relax is religion.
Just because some religions practice this, is not anymore “religious” than someone kneeling is Catholic.
I know. That's the gist of what I already said.