In China, until recently, all toilets were basically squatting toilets, yet octogenarians had no issue squatting to use them... how old are you that you can't do for 5 minutes what an 80 year old can do several times a day?
Also, I'd like to point out the differences in length of time between taking a shit and a normal 8 hour work day.
I'm not saying this is impossible, but I understand the trepidation.
And we still don't have any arguments supporting either position. I do squat for a few minutes every day to facilitate my squat lifting workout but don't see an inherent benefit. I suppose one can argue that it has been a natural movement for so long that our bodies may be genetically designed for it.
My mobility is still poor compared to what it was when I was a child, but at 38 I'm now finally more flexible again than I was at 25, maybe more so than at 20, and it's great to not feel constrained by weird movement patterns.
long-limbed people have more difficulty with this, while shorter-limbed people don't have difficulty with this after a little stretching