I had a memory that it was related to a prohibition on being able to put "Something II " onto the part 1 register unless you were the owner of "Something" but not only have I found nothing whatsoever to support that, we don't even know if the boats concerned are on the part 1 register. The closest I found in schedule 1 of the Merchant Shipping (Registration of Ships) Regulations is a prohibition on:
...which wouldn't seem to cover it
So unless someone can provide some supporting evidence for this theory I'll say discount it
