In a recent Yoga Orkney Tuesday session we practiced up to chair pose (Utkatasana) and explored some similar shapes seated and lying on our backs. It raised some considerations about how the posture tends to be demonstrated (picture A) and why it might be that your version of the posture doesn't look like it does in the pictures*.
*spoiler alert - it's not you!
Picture A: Squat position - Chair pose (Utkatasana)
Variations in the length of the thighs and the shins alter how much one needs to tip or hinge forward at the hip. How much movement we have in our knees and our ankle joints will also dictate how far we can drop down to the floor. Ability to manipulate the various curves in the back also impact how upright we are in the torso and how straight the spine appears from the side. Bringing the arms in line with the ears alters what happens in the upper spine and depends on how your shoulders like to move.
In order to make the shape in Picture A, you would need to be 1) hypermobile in a number of joints (that carriers a different set of considerations) or 2) have the exact genetic proportions to carry off this shape. If you've had an injury or replacement of one of the joints mentioned that will have an impact too.
If you aren't any of those things chances are your posture looks a little different. maybe you don't sink as far down, maybe you hinge forward at the hip, maybe the arms don't fit alongside the ears, your feet are further apart or turned out (you get where I'm going)... All of those options should (and are) perfectly reasonable to expect.
I reckon when we use this shape in real life as opposed to a Yoga class, you might be holding a heavy object up high and would split the feet or you would be lifting something up from a seated position and wouldn't be staying still for long. Even in the clean and jerk in weightlifting, they are pretty quick to split the stance when they get the weight over their head and they don't hold it over their head for long!
The fitness industry at large is catching up with research and beginning to incorporate new learning into trainings and workshops and an individualised approach will be more common as teachers incorporate these learnings into more sessions.
This short video below explains it really well.