(Of course, we should be asking RH... but nevertheless)
EPEL 8 has several issues regarding packages without corresponding
-devel. E.g., libXvMC, libbluray.
AIUI, certain -devel packages land in the CodeReady repo. But these two in particular are not actually in the CodeReady repo.
And FWIW, you can always get the src RPMs and build them yourself to get the -devel packages. Generally I'd agree that you should not have to do this, but based on the private comments in that BZ I'd guess that that may be your only option at this time.
HTH
--
Kaleb