Great attention to detail. That’s actually fine, as far as I can tell. It’s worked in the past, at any rate.
If you do a search via pacman of everything starting with xf86, you’ll get a lot of hits. This is a naming convention left over from when these drivers were part of the XFree86 implementation of the X Windows system, which was the standard on Linux boxes from on or after 1991 until sometime around December 2008 when it had its last release.
I actually remember getting in fights with XFree86 back when I tried to run Mandrake in the late 1990s.
pacman actually indicates these drivers are part of the Xorg package (Xorg was a fork of XFree86).