There is nothing wrong with the term “Full Expression of a Pose” except when it is misused and viewed from a physical perspective lens. Then yes, this term promotes comparison of bodies, postures and perfect alignment. It does not take into consideration individuality and musculoskeletal differences.
The phrase on its own is not flawed, it is the incorrect focus, on the emphasis and the application that is incorrect.
What many fail to understand is that there is a whole process that begins at a cellular level. It is not just the physical body working towards a pose. To arrive in a pose requires a thought process which will reflect an emotion/sensation which in turn creates a reaction or action within the body.
The mental body to think and discern, the emotional body to express and feel, the physical body to listen and adapt. In yoga these faculties always work together as a whole and to separate them while teaching, would be a disservice towards a student’s practice and growth of yoga.
When these centres are in alignment with our prana/energy and most importantly our breath, we then reveal our “Full Expression of a Pose”
As yoga teachers our cues and instructions ought to reflect every aspect of the practice while respecting and maintaining the individual's needs on the mat. Our yoga trainings must shift their focus from asana based teachings to one that encompass the full spectrum of Yoga. Our vocabulary or use of language needs to be crystal clear and concise.
For yoga to be accessible our understanding of its philosophy needs to move beyond the physical. .....Yoga does not discriminate nor exclude and therefore our teachings ought to reflect these sentiments too.
The responsibility lies on us the teachers to teach purely within the context of Yoga.