Create pull request starting from a tag through UI

Stash doesn't let a user create a pull request from using a tag as the source using the UI (get the error "You cannot create a pull request with a tag")

I can't see a reason for the source not being allowed to be a tag (the destination need to be a branch, but not the source) and this does work through the REST API.

Use case is to merge a specific release into a development branch or master after its gone live.