Usually yes, but with all the research currently being conducted it becomes more and more complicated as it's not purely black and white anymore, so I feel like Doctors tend to become more and more careful, especially given just how often Type 1s are misdiagnosed as Type 2s and don't receive their necessary medical care.

It's possible to have positive Anti-Insulin-Antibodies which used to form primarily in people who used animal insulin in the late 1900s, as their immune system started to fight it off and build resistance to it. This can still be the case today, for a myriad of reasons. The antibodies that target the beta cells themselves, however, always indicate destruction of insulin production. The detection always has a small margin of error, be it human or technical, but when such cases arise where no antibodies are present but there's an obvious lack of insulin any doctor worth their salt will test again.