Betta Fish: Flaring at the filter?

I’ve never owned a betta that flares regularly aside from Napoleon, but he has this strange thing where he’ll swim directly under the filter flow and flare at the glass until he’s pushed away, and he just swims away as if nothing happened. He enjoys swimming underneath it but I’ve never seen him flare at it, should I be worried?

Also ignore the uprooted plant, I was gonna replant it but he built his bubble nest using the corner so I felt bad lol, next water change