I have just got a 2009 Amara 560/6, recieved the same advice from my dealer, which seemed quite sensible to me, they said instances of the microwave "jumping out" had been heard of, maybe not just Amara's but maybe any van with built in microwave.
I do not find it much trouble to remove, only a trim panel to unclip and a socket to disconnect, how difficult can that be against the potential for damage should it decide to remove itself whilst being towed.
Regards
Mark