No, v3 is a release with breaking changes:
This release includes several breaking changes; read the full migration guide here. It's worth mentioning that many of the breaking changes are updates to API endpoints and only affect third-party tools that integrate with Immich's API. For the vast majority of users, updating works exactly as it always has.
https://immich.app/blog/v3.0.0-release
That's why the major version was increased, it implies breaking changes in semantic versioning, which Immich is doing since v2 apparently:
Given a version number MAJOR.MINOR.PATCH, increment the:
- MAJOR version when you make incompatible API changes
- MINOR version when you add functionality in a backward compatible manner
- PATCH version when you make backward compatible bug fixes