The original Haulmark VIN had expired, and rather than re-activate it, a new one was issued.
I suspect that was because it takes a little time for the old VIN to be reactivated. I suspect the previous owner was a little impatient.
When Peter registered his trailer, the paperwork and inspections were done, Peter was advised to come back later. He did and collected his plates.
As with any government department, it all depends on who you talk to and what you say.