In the UK it's called "remission" and is formally declared (like a peace treaty in a war!) when you've had 2 HbA1c readings of less than 42 in a row. This is because, at this level you are considered to have very good control and be out of the danger zone for all the T2D nasties: as long as you stay at that level of control you will, indeed, be okay.
But that's often a flash point for T2's: "Well, I'm cured! I can do anything I like!" they think - and they return to the Eatwell Plate and take up going to the gym twice a week (with those lovely sports drinks), and have the occasional slice of cake at birthdays and Christmas and, because they're "in remission", no-one's really looking at their control anymore... so they slip.
It's not anyone's fault. It's that until really very recently, Type 2 Diabetes was seen as a progressive, life-changing disease that had no cure and no real management strategy. The notion of remission - of the T2 Diabetic taking active control and self-managing their disease is a very recent one: we're still advised there's no need to test our BG regularly, we're still given the Eatwell Plate as an example of a healthy diet, we're still not counselled about what to actually do when we hit the magical "Remission" day.
Which is why forums like this are so important: lots of people here are in remission and have maintained their control. This forum isn't just about managing diabetes, but keeping it under control for the rest of our lives.
Congratulations to you for accomplishing the first stage of your journey!
Final thought: The "get fat again" is because people who have T2D are insulin resistant. And a sign of insulin resistance is a spare tyre many of us (not all) carry around our middles. If you have had a diagnosis of T2D and get that tyre back, it's a clear danger sign. That's all he meant.