External headphones volume control

I am using AIAIAI headphones on iPhone 12 mini. It seems like the phone has internal volume control on because the volume in my headphones does not increase after 11 points on the volume bar. So the last 5 volume up clicks have no efect on actual volume whatsoever. This is not an issue on any other devices like laptops, computers and androids.

I tried setting up custom audio setup but it is not supported for anything besides airpods and beats.