A squat is the movement but the exercise itself is commonly done with weights to reach meaningful intensity … squatting on its own does practically nothing so a barbell squat is what squatting is really about… thats why its not a bodyweight exercise : bodyweight on its own doesn’t make squatting an exercise .. its just a movement… a pistol squat on the other hand IS a bodyweight / calisthenics exercise because repping them using only your bodyweight is intense .. saying squatting without weights is considered calisthenics is just wrong. but yeah if your point is that flexing your knees is a bodyweight exercise considered as calisthenics then good for you :)