Minor Description
With OAK-9134 the nt:frozenNode definition was changed and new repositories created with Oak 1.34 or newer create frozen nodes that are not referenceable anymore.
The migration component in oak-core (org.apache.jackrabbit.oak.plugins.migration) always copies versions from the source to the target as is. That is, a migration from an old repository to a new one may result in frozen nodes that are not referenceable but still have a jcr:uuid property. The migration should respect the nt:frozenNode definition on the target and omit the jcr:uuid property when the frozen node is not referenceable.
Similarly, the oak-upgrade component has a side-grade feature that needs adjustment.