They just changed the versioning scheme; it used to be that e.g. 9.3 -> 9.4 was a major version (i.e. can't be upgraded in-place). Starting with PG 10 major versions are now 10 -> 11, etc. I don't believe the major release cadence itself changed that much
It seems like they fell more inline with Semantic Versioning when that format came in vogue. Semantic Versioning is what most devs expect now; it makes sense to communicate the version in a format that has a broadly understood meaning for devs.
I think there is no semantic versioning anymore, they just release one major number version every year, regardless how large and backward compatible changes are there.
