As I understand it, that subdirectory was a deliberate change by upstream to allow for parallel installation of different versions. As it was worded in the social media post Lunduke made after interviewing Weigelt: “Per-ABI driver directories (allows distros installing multiple ABIs at the same time, eg. for smoother upgrades)”.
As a packager, I think this does not quite solve the parallel installability problem because the binaries in /usr/bin will still conflict (also with X.Org because even the Xorg binary has not been renamed) and hence force any parallel-shipped packages to use Conflicts instead of being parallel-installable. Unless the binaries are renamed by the package (which makes them no longer drop-in replacements) or put in some nonstandard directory.