How is it determined if a package needs to be rebuilt for a newer Fedora version?

[Richard Shaw]

I see regularly where new(er) users wonder why they see packages
installed with dist tags from previous versions of Fedora.

I understand why this occurs but now that I've gotten into building
some of my own packages I started to wonder how it is determined if a
package needs to be rebuilt or not.

Do we rely on the package maintainer to make a call or is there some
definitive way to test a package?

Thanks,
Richard