I have visited this rock many times. I am not a scientist or linguist, just a hiker. I will not speculate as to its meaning or origins. I will tell you that I am convinced it is not a hoax in the ordinary sense of the word. The rock is extremely hard, durable, and excrutiatingly difficult to carve or etch. (I have taken samples from the surrounding area just to see how difficult such a task would be.) Also, the area is ravaged by wind and bad weather, blistering heat in the summer months and bitter cold in winter. It is not a comfortable place to spend a week or two etching BS into a rock. Another thing I find remarkable about the place is that the rock sits at the bottom of a ravine that leads up to a mesa, upon which sits the ruins of a clearly identifiable ancient village of some kind, such as those common to Anasazi or Toltec.
There are other etchings and hieroglyphs nearby, most of them are not as deeply carved into the rock, yet it is clear many of them have been there since ancient times. There are also many vandal or hoax etchings in the area, (grafitti) but none of them rival the kind of work that has obviously gone into the inscription of this one peculiar rock. If you visit, please treat the place with respect. It may be a hoax after all, but the sheer amount of effort involved convinces me that whoever did this was very serious about the work regardless of what it says or means.