New versioning schema for docker tag?

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Describe the bug
Looking at the new version v3.9.0 the versioning of the docker tag changed, without noticing it somewhere.
Everywhere in git v3.9.0 is used(tags, release ...), but on dockerhub it now changed from v3.x.x to 3.x.x
Was this intended, so I update my renovate bot config to the new versioning, or is it a "bug"?

To Reproduce
Steps to reproduce the behavior:

1. Go to 'dockerhub'
2. Look at the tags of v3.8.0 and (v)3.9.0

Expected behavior
Just wanted to know if further versions also use this schema, and it is not an unattended behaviour.