In this article the author explains why squatting the deadlift (i.e. deadlifting with a too upright posture) is bad.
This in turn both creates unfavourable leverages that cause more stress on the lower back AND decreases the amount of weight you can lift since your centre of gravity isn’t placed in an optimal position.
I can't understand the second one very well. Why isn't the centre of gravity in an optimal position? From what I understand, the general rule (both in squat and deadlift) is that of having the centre of gravity over your mid-foot.
If you do a back squat like in the following picture (taken from here), the centre of gravity (which, with huge loads is given by the barbell position) is above your mid-foot with a quite upright posture. So, it's fine and I think I understand that.
What I can't understand is: why can this not work for a deadlift too? Since you place the barbell over your mid-foot in the starting point, the centre of gravity will be over it. How can a too upright posture move (and in which direction) the centre of gravity in a bad position?