It is a difference if you are talking about Boxer or In-line engine.

Boxer (Flat twin) 2-Stroke engines uses the same Crankhousing room. So it makes no sense to use 2 carbs. One is enough.

In-Line 2-Stroke engines have single crank house space. Both chambers are seperated by the middle bearing with seal ring.

Here you can use 2 carbs. But mainly the manufacturers uses Y- intake header. Cheaper, but there is space for some tuning.