In Tai Chi, as well as in Yoga, the outwardly-visible is never the whole story.
The movements of Tai Chi forms are not routines to be learned for the sake of accomplishment and performance, but rather to train energetic and mechanical alignment and efficiency, as well as to cultivate a quiet mental focus or intention.
The same underlying premises and directives exist in all Tai Chi postures and movements. What is to be done in one particular movement is also the imperative in all the others.
To borrow the great Yogic maxim: Sub Ek. All One.
The reason a skillful Tai Chi player appears calm and relaxed is because there is nothing exciting or compelling in their experience of executing the forms. The quiet moment before commencement is present throughout the entire sequence.
An external-only approach to playing the Tai Chi sequences is like walking around a tranquil and still lake. The internal approach means to become the lake.
Whether you count 8, 24, 48, 73, 97, or 108 forms in your Tai Chi sequence of choice is not relevant once we are practicing the internal aspects.
There is only Yin and Yang, the Tai Chi, and as we allow Yin and Yang to flow we hold to the Wu Chi in the center. We carry and become the stillness around which movement occurs. We become the lake, rather than merely walking around it.