Assuming that with “core packages” you refer to the packages in the three repositories starting with “core_” I think the concept of versioning according to semver collides with the proposal to use the same MAJOR.MINOR.
If there is a breaking change in e.g. core_perception you would level its major version following semver. Why should that also result in requiring to level all the other core packages? Users of these APIs shouldn’t be broken. So imo requiring MAJOR.MINOR to be the same eliminates the advantage of versioning the repositories individually.