Even in these badly-framed videos I see no excessive anterior pelvic tilt. Who told you that "excessive" lumbar extension causes quad tendon pain? How was this mechanism explained? How do you know that you in fact stand normally in lumbar overextension? There are about 9000 other ways to explain quad tendon pain without resorting to something as exotic and arcane as "Anterior Pelvic Tilt." But if you keep trying to squat with lumbar flexion, you are going to actually hurt yourself.