I've lived low-carb as a T1 and my blood sugar was very stable. I would still take sugar to stabilize levels when dipping low. A completely ketogenic diet would be very hard for a T1 and not a sensible goal. Insulin management was simpler, but still required. On many days I would just do the one injection of long-lasting insulin.

While the scantly researched health risks associated with a ketogenic diet remain, the diet is very effective to keep blood sugar stable. A low-carb diet protects most people from T2, and people with T1 profit from simplified insulin management.

For a T2, eating ketogenic could be healthier than eating carbohydrates. Depending on progression, they would recover quickly and not be a T2 anymore.