Current Fedora MBS does not respect a buildonly attribute (implemented in issue #1307) in a modulemd-package-v3 input. As a result binary packages built from these components presents in the module build's artifacts.

Example: perl-Test-Deep component has the buildonly flag set tru true [https://src.fedoraproject.org/modules/perl-CGI/blob/de607bc89eae483321e0ef6495ef0959255bbdcc/f/perl-CGI.yaml#_90], yet the binary package perl-Test-Deep-0:1.130-5.module_f35+12154+05bebac9.noarch is an artifact [https://kojipkgs.fedoraproject.org//packages/perl-CGI/4.51/3520210611044039.7b434ab7/files/module/modulemd.x86_64.txt].

Maybe the problem is that the module already defines a filter. According to the specification, buildonly binary packages should be filter in addition to the explicit filter list.

I also believe the same problem is with modulemd-v2 input format as can be seen in an older perl-CGI:4.51:3520210303092153:7b434ab7:x86_64 build.