This does introduce a slight behavior change in that tags that probably should have been excluded before are now definitely excluded. I think this is the correct behavior and people shouldn't have been relying on the previous behavior where tags without the requested prefix were being considered valid tags, but it is a change.
A fix for this issue: https://github.com/mathieudutour/github-tag-action/issues/143
This does introduce a slight behavior change in that tags that probably should have been excluded before are now definitely excluded. I think this is the correct behavior and people shouldn't have been relying on the previous behavior where tags without the requested prefix were being considered valid tags, but it is a change.