I 100% agree on the latter (the tag != release is more of a project management issue), and the same concept applies to containers and their digest hashes. The main issue at the end of the day is the human one: most people don't like looking at hashes, nor do they provide context of progression. I would say "give both" and make sure they match on the end user side of things, but tags are the most common way (open source) software releases are denoted.