Latest of anything is RARELY stable. It's stable until someone hits a critical bug in the new release, then there's a new version, but your image is still running the older version. That's why we invented the concept of LTS tracks.

> I think the problem with specifying just 'apline:3' is that it is an ambiguous statement.

It is not ambiguous in Docker Hub land. It's a very widely used convention that means "give me the highest 3.x.y"