don't know if there is a complete answer to that question. as the muscle and tendon are continuous and integral I don't think any clinical test could pick that up. you can of course differentiate gastrocs vs soleus components as gastrocs is a two joint muscle while sole us is a one joint muscle.

it could also be a bit of an academic point - when a musculotendinous unit is allowed to shorten probably various changes happen simultaneously: the number of sarcomeres in series reduce (muscle only). abnormal production and alignment of collagen fibres throughout the connective tissue (so epimysium, perimysium, fascia and tendon). then ther may also be articular changes at the ankle due to the lack adequate dorsiflexion occurring)