Repo made for testing versions in format SERIES.MAJOR.MINOR.PATCH, eg. 7.1.0.0
Tested using a package petr-heinz/packagist-version-test2 registered on Packagist and semver.mwl.be.
Results:
Packagist parses it as MAJOR.MINOR.PATCH.BUILD, meaning Composer would not expect a BC break between 7.1.3.10 and 7.2.0.0
See the difference between ^7.0.0.0 and >=7.0.0.0 <7.1.