Hmmm, I never thought of that angle. You are talking about home country insurance yes? Medical "fly me home if I break my leg" type of insurance?
That might be a problem if they want to get really nasty: "What, Mr. Mingh, were you doing riding a vehicle for which you were not qualified?". Western insurance companies could use that one to get out of their side of the deal, yes.
You'll have to think about that one. I haven't any suggestions. Although perhaps, if it came to a push, "I did my test and passed in Mongolia, and here is the documentation", might help a bit.
On another point, make sure you read the small print regarding vehicles. Even if they allow you on a motorcycle, there may be a restriction on the size of the machine. This was the case for me. I had to pay extra to get me up to 600cc.
Around the world 2000-2004, on a 1993 Honda Transalp