Actually, according to the MSDS it's about 70 percent ethylene glycol and the remainder is propylene glycol and corrosion inhibitors. So it's still highly toxic. My guess is they added just enough propylene glycol to get the freezing point down to an acceptable level. Straight ethylene glycol freezes at around +9F/-13C.
The problem I see with running straight glycol coolant is that both propylene and ethylene glycol have a lower specific heat than water. Cooling systems are designed to use a glycol/water mix, and aren't going to work as well with straight glycol. This may not matter most of the time, but could be a serious issue under severe conditions.