As per our image policy, patch versions are updated in-place and can include bumps to patch versions of included software as part of the process.
The 14.3.0 image was replaced with 14.3.1 recently:
It is better to use the macOS orb as it contains logic to fuzzy match Ruby versions, allowing you to just specify a major.minor version, rather than working down to the patch level (patch images will retain the same major.minor versions of Ruby):