Yes the needle length is not your problem and yes you’re getting absorption if the oil is going in. For small muscle groups I use 5/8” 25ga. For glutes I use 1.5” 23ga. I don’t do subQ it’s for pussies (humor).
I use 1/2 inch (quads & deltoids) and I’ve never had a problem. There have been occasions where I didn’t get the needle all the way into the muscle and still no issues.