VRChat SDK Worlds 3.1.11 should be VRChat SDK Worlds 3.2.0 according to Semantic Versioning.
According to VCC docs, VRChat SDK follows Semantic Versioning 2.0.0.
According to Semantic Versioning 2.0.0 rule 7, minor version Y (x.Y.z | x > 0) MUST be incremented if new, backwards compatible functionality is introduced to the public API.
In VRChat SDK Worlds 3.1.11, VRChat introduced five features: load remote images/strings, play back MIDI data, simulation time access, and OnDeserialization with DeserializationResult.
This is new, backwards compatible functionality of UDON API, which is part of Public API, so VRChat must increment minor version in 3.1.11 so it should be 3.2.0.
I think it's not required to increment minor version of new UI feature is added (e.g. udon graph editor improvements in 3.1.9) because UI may not be a part of the public API.
However I think addition to UDON API is new functionality to the public API so VRChat should increment minor version.