Is it true that sagging cheeks after facial contouring are ultimately caused by the incisions?

While studying facial contouring, I heard that the moment a large incision is made inside the mouth to examine the bone shape, the flesh and bone separate, making it difficult to prevent sagging later on, no matter how well they are reattached (separated). So, if I go to a hospital that performs surgery using only minimal incisions to prevent separation, would I not have to worry about sagging?