I have to admire the pedantry today
So, the facts - here is my Policy wording : -
3. Having an MOT certificate
There must be a valid Department for Transport test
certificate (MOT) in force for the motorcycle if one is
needed by law. In the absence of a valid Department
for Transport test certificate (MOT) when one is needed
by law all cover under sections A and B of this insurance
is cancelled and of no effect.
That leaves just section C, 'Liability to other People' as the only risk where cover remains. However there are numerous general exception clauses relating to ensuring the bike is roadworthy, properly maintained & conformity to manufacturers specification, which create potential obstacles. Personally, I have fully comp insurance & all the trimmings to ensure every aspect is covered - no MOT means a major chunk of liability is excluded.
So I understand your argument Wapping & accept that you have a valid point, if a tad academic in this context. I have no idea of the Police stats, nor am I particularly interested, but I do know there are plenty of prosecutions for the absence of an MOT, mostly from Camera/ANPR around here as plod are thin on the ground in our rural patch.
Poor OP, we have digressed enough. Bike off the road without MOT could affect the machine's value & could, in certain circumstances, lead to a claim being rejected. Does he need to advise his insurers? - that's down to interpretation of the policy wording, so needs checking out. If in any doubt pick the phone up & ask.