Why must I use scale_vaapi with kmsgrab, but hwupload with x11grab when using vaapi with ffmpeg?

I am wondering why, when using vaapi with ffmpeg, if I use x11grab I must use -vf format=nv12,hwupload but with kmsgrab I must use -vf scale_vaapi=format=nv12 instead. In particular I want to know 2 things. - Why is it this way? - Is there any way to use normal filters (like eq=brightness=50 or zscale) with vaapi when using kmsgrab? Because the dilemma that's causing me to ask these questions is that I need to do some color corrections and filters seem like the best way to do that, but I'm unable to use filters when I'm using kmsgrab because scale_vaapi breaks other filters, and I even tried using some obscure filters like procamp_vaapi which shuold allow me to do the same things as eq, but I couldn't get it to work. my kmsgrab command: ffmpeg -y -device /dev/dri/card1 -f kmsgrab -i - -vf 'hwmap=derive_device=vaapi,scale_vaapi=format=nv12' -c:v h264_vaapi -qp 24 output.mkv