I always heard it referred to as delayed onset type 1 by endocrinologists. It is possible it was referred to as 1.5 at some point though. Most of my terminology comes out of late 90s early 00s when I was participating in medical studies for diabetes. I'm obviously still diabetic but I just see a GP now since specialists are expensive and hard to get in to see. So I don't have as much up-to-date terminology and things have changed a lot in the last decade.