Depending on the insurance company, vehicle (make and value), the insurers have different requirements.
I'm a bit surprised their insurers didn't expect a Thatcham 1 alarm for the vehicle you describe, even though as motorhomes go it isn't one of the more expensive ones.
Ford based ones seem to have been especially targeted recently- at least one of the insurers sent a circular out regarding changes in conditions. It didn't impact us so I don't recall the details.