Why would a Tummy Tuck be performed without Diastasis repair?

I recently had ventral hernia repair with an abdominoplasty. I have a very large diastasis, that was NOT fixed. I still have a huge protruding area in my abdomen. I'm unhappy with my results, now my Plastic Surgeon says he can correct the diastasis. The reason he gave for not fixing it initially was "we don't fix it at the same time as a hernia repair because the muscle could stick to the sutures and cause a problem". Should I let him redo the surgery, another Plastic Surgeon...or just leave it alone?