This is not a real issue causing any trouble. I just think it's a good idea to report it.

See: https://pkgs.devel.redhat.com/cgit/rpms/gimp/tree/gimp.spec?h=stream-gimp-2.8-rhel-8.10.0#n364

The string "use_poppler" is always true from rpm point of view so the bcond for poppler does not do anything in this part. This works because the old version RPM in RHEL 8 thinks this is a string even if it's not enclosed in parentheses.

I realized that when I tried to run rhpkg prep with newer RPM.