Ankle, calf, and Achilles’ tendon mobility is a key ingredient in squatting and the quick lifts. Tightness and lack of mobility in these areas can cause a host of squatting problems, such as the knees coming in, weight coming forward onto the toes, and pronation of the foot, among others. In short, ankle tightness can ruin an otherwise good squat. A particularly strong person might get away with bad ankle mobility on a back or front squat by muscling out of the hole, but a more technical lift, such as the overhead squat, will stymie them. Ankles and calves especially are very strong. They bear thousands of pounds of pressure daily. They need and can take aggressive stretching and mobility work.
Give them some attention. Your lifts, and your knees, will thank you.