Jason, the first photo tells us a lot. Dawson was found in the right hand area described here as class 4-5. We'll never know for sure what happened, but this is consistent with the speculation that he was looking for a shortcut back to camp. The photo you posted is taken straight on, and it makes the slope look much steeper than it is. While it's not trivial, that slope is nowhere near vertical, especially at the top. I'm confident that he was trying to climb down, and that he didn't just walk to the edge and fall off.