Start here: the scar, not the surgery, is the defining problem
Back skin is thick, and the closure is under tension every time the arms move, reach or lift. That combination makes back scars widen and thicken more reliably than scars almost anywhere else on the body, and in post-weight-loss patients whose skin quality is already compromised, the result is frequently a wide scar that becomes a permanent feature rather than a fading line.
This is why scar placement is the decision worth negotiating hardest, more than technique or even surgeon choice in some respects. Positioning the excision exactly where a bra strap or swimwear band covers it is the only concealment available, and it must be planned with you standing and wearing the actual garments you use, not estimated from memory or marked while lying on an operating table.