Effect of Medial Arch Support on Displacement of the Myotendinous Junction of the Gastrocnemius During Standing Wall Stretching, Jung, Koh et al; JOSPT 12-09.
John Madden was in the Oakland Raiders locker room back in the 70's giving his pregame speech, when the players started asking too many questions. He blurted out, "Don't worry about the horses, just load the wagon!"
That's a good analogy for function. Don't get tied down in what individual muscles are doing. DO make sure the athlete can load the wagon. If the athlete cannot sufficiently dorsiflex, one of the most powerful musculotendinous units in the body is not getting loaded. It can contribute to everything from tibial stress fractures to glenohumeral impingement.
This study found that in athletes with a pes planus foot, dorsiflexion improved an average of 6.4 degrees by supporting the longitudinal arch. A little adhesive felt in this population goes a long way.