Is it necessary to attach the muscle to the chest wall when removing an implant that was placed under the muscle? (photo)

I think the deformity you are experiencing is only partly related to repairing the pectorals major muscle back to the chest wall. What you have is scar tissue still attached to the bottom part of the breast and skin. You can wait until the scar soften over time which can take about a year. Or, if the scar tissue is scar capsule, you will need to have your breast tissue released from the scar which may be still attached to the chest wall. In other words, you need a scar release. I have a lot of experience with this problem. Please be assured that it can be corrected.

Implant removal can lead to breast deformity due to the implants effect on the surrounding tissues over time. It is hard to make a comment without a physical exam.  Hopefully a capsulectomy was perfumed. The pec major muscle could have run inferior to the nipple areolar  and by attaching it to the chest wall resulted in tenting the breast up under the NAC in a standing position that is hard to detect in the OR. Simple release of this attachment might correct the whole issue. Most definitely discuss your situation with your PS and state your concerns.

It is possible that the muscle is causing this deformity through action on the capsule that is attached to subcutaneous fat.  Does the deformity worsen with muscle contracture?  If so, then a muscle release may be necessary.  Either way, a lift would be necessary to correct your breast shape and nipple position.