Use cases --prebuild and --name are not very intuitive to use and they should work with full path to (s)rpms. Rework needed. Approaches in the comments
Proposal: We change the help text for -n/--name like:
Use local files .spec *.src.rpm in current dir. When used with --rpm-spec also accepts complete srpm filename.
And updates manpage and code accordingly.
fixed in 254817c46a5ad15170e32f2e97765bd782f63afb according to comment:1
Thanks for report :)