I think it was concern about high the cliff was.
I have heard a variety of theories:
1. How high the cliff was, and Jake doesn't like heights.
2. The risk to Jake (but then, why did they let Heath do it?).
3. Jake wasn't on the set. This scene was filmed in the 2 week period when he left to go attend to other business.
Thanks for the pictures, Chrissi, and beautiful rose, Clarissa.
L