Trying to take an unconditioned person and telling them to hold a deep squat like that for hours = injuries all over. They'll lack ankle flexibility and whatnot.
A person unused to squatting will often have problems holding a squat for 30 seconds, if able to get down into a squat in the first place. I very much doubt that injuries would be a problem simply because the position is nearly impossible to hold for prolonged periods until you've developed the flexibility needed.