If you're in love with this muscle, then here are some resources to give you a better perspective of the role that it plays.
1. Gil Hedley demonstrates the anatomical relationship between the Diaphragm and the Transversus Abdominis
Does this confirm or refute your current beliefs?
2. Stephen Brown and Stuart McGill examine the relationship between ultrasound and electromyography measures of force and activation to evaluate abdominal wall contraction.
Take a read through the paper. Although I'm not well versed in the role ultrasound plays in examining muscle contraction, the authors do explain the complex dynamic interplay between muscle contraction and adjacent muscle layers. Specifically, that the contraction of a particular muscle may influence its adjacent (superior and/or inferior I suppose) muscles and that movement of these muscles may not directly relate to force of contraction.
What do you think?