Let take a different take on this. I think your GP is saying
Very long term type2 can result in the bete cell being kill by a different process then type1 and hence the inslin levels drop to the levels seens in type1. By saying you have both type1 and type2 the likelihood of anyone reading your notes providing the correct medical care has been increased.
Not that he has seen test results to prove your bete cells are being killed by your autoimmune system.Provide treatment as if you have both type2 and type1
Very long term type2 can result in the bete cell being kill by a different process then type1 and hence the inslin levels drop to the levels seens in type1. By saying you have both type1 and type2 the likelihood of anyone reading your notes providing the correct medical care has been increased.