Your question title asks if you can run against a glass door you can't see through but the meat of your question asks if it's true that someone might get hit with a glass door you are opening when it isn't transparent, correct?
To answer though, I doubt it would take a study for either one of these, as they seem to be fairly common sense things (I could be wrong, government will fund studies on the dumbest, most self-evident subjects from time to time). I stand corrected: here is a study done on walking through glass door injuries. In fact, it is such a concern that the state of New York has a section of their building code dedicated to it: PART 47 TRANSPARENT GLASS DOORS. Can't seem to find anything on obscured glass door injuries though.
If you are approaching a clear glass door, you may not see the door and smack into it. You could even hurt yourself severely enough to require surgery.
If you are approaching a door that is not transparent (for whatever reason, building material, flyers, etc) you run the risk of 1)hitting someone on the other side with your swinging door or 2)being hit by someone opening it onto you from the other side.
Since many non-sliding glass doors have a metal separator with a handle in the middle of the door, a person will most likely SEE this as a door (and the people on the other side). I suppose it all comes down to what kind of a glass door it is: a divider or handle or some sort of appendage to suggest a door, or a sheet of clear glass that is begging to have your nose get squashed upon.
If the glass door is then obscured with materials, people on the other side are no longer visible, and for safety's sake (and LIABILITY issues), the university errs on the side of caution, I would imagine.