Why does my bird do this?

My lovebird, Zac, (don’t let the name throw you, I’m pretty sure he’s a girl) is 11 months and 20 days old. He has a small pink swing hanging from the roof of his cage that has a solid base and a curved top. The swing is a few inches shorter than he is. The thing is, he likes to sort of curl up on the bottom of the swing and rub his head against the bar. He doesn’t do it at any particular time, and it seems to be relaxing or comforting for him. He has two other different sized swings and many other perches and toys that he uses regularily. He’s barely ever alone in the house and most of the time he’s out of the cage being played with or just flying around (supervised). He has a wooden nesting box that he uses as well. He’s been doing the thing with the swing for a long time now, and I’d like to know why. Have any suggestions? P.S. I know birds can practice “self gratification” but I’ve seen other birds do that and it doesn’t look similar.