The fascia that some surgeons attempt to to lift off of the muscle is a very think layer and is difficult at times to separate form the muscle. In short, it is essentially the same as a sub-glandular augmentation. I do think that the only way to alleviate the animation of the implant when flexing your muscles is an exchange for above the muscle though.
Subfacial or subglandular implant placement
If your breast implants which are under the muscle have a lot of physical distortion when you flex your pectoralis muscle then the lower medial portion of the pectoralis muscle was not released properly. With most submuscular implant placement if the surgeon does not release the lower origins of the pectoralis muscle when the muscle contracts it will pull the implants up and displace the implants laterally. All breasts will move when you flex your pectoralis muscle even breasts that are natural and without breast implants. Implants placed in the subglandular or subfascial plane may move slightly less but because you lack additional soft tissue covering the upper pole of the breast will look considerably rounder and more ball-like compared with submuscular placement. The main difference between subfascial and subglandular placement is the issue of support and preservation of the supporting ligaments of the breast. The breast is naturally attached to the fascia that covers the pectoralis muscle. There are numerous ligaments called Cooper's ligaments that attaches the breast tissue to this pectoralis fascia. In a subglandular breast augmentation these Cooper's ligaments are cut so the breast stretches and falls more over time. If the implants are placed subfascially these ligaments are still attached to the fascia so theoretically better preserved but not as well as if you did not disturb them in the first place as in the submuscular plane. So in short if your implants currently is under the muscle but there is significant distortion of the muscle you need to revise the pocket and the muscle and it will not distort in the same way. Implants placed via a transaxillary approach will tend to distort the most since it is difficult to control release of the lower bands of the pectoralis muscle from that approach.