A client who comes in with calf tightness and ankle stiffness can't be clumped into the catch all group that they need more ankle rocker or to just stretch out the posterior mechanism.
In all likelihood they probably don't have a stable enough foot/arch and are passing their body mass over that unstable structure, collapse ensues before ankle rocker is completed during stance phase of gait. Thus, the body goes into a strategy the next joint complex up the chain and attempts to gain stability at the ankle complex and the most available tools, the posterior mechanism. The foot should be stable and the ankle should be mobile through sagittal ankle rocker. When the foot is unstable, things often switch; the once mobile ankle rocker shifts towards stability attempts. Not everyone needs ankle rocker work ! Don't force it, make them earn it once you find the root of the problem. In a huge chunk of the population, that stiffness and loss of ankle rocker is there as a coping mechanism to find stability. Don't take it away from them !
PS: raising someones arch with an orthotic doesn't earn any stability, it is borrowed, it is false, so keep that in mind. Not that it doesn't have value or a purpose, but nothing has been intrinsically fixed, only extrinsically and that cannot be forgotten. Someone has to pay for these loads coming into the system.
-Dr. Allen's rant of the day