Probabilistically normal BMI and under 30 would indicate type 1. I never said anything about it being age restricted. There are just more cases. But you need IA2 and GAD antibodies.
Without IA2 and GAD antibodies, Teresa May could be thin type 2. She couldn't control her blood sugars with diet (she was pictured eating hot chips on the campaign trail over the weekend, so I'm not surprised) so she went onto insulin. More and more thin type 2's, who have more type1 like symptoms, are put on insulin and told they're type 1 without any sign of antibodies.