I would need to double check but I think there is a reason for that. What is the drop (metres) on the other side? I think there is a building regs rule that says that if you have to retain or barrier more than 0.6m height, you need more than a fence i.e.the structure needs to act as a balustrade to prevent a fall (which a fence along won't do). Hence the level slopes down on your side to reduce the step.
I had a similar request from a developer on a project I'm current working on, regarding avoiding drops over that height.
(again, need to double check the clause so don't quote me on the specifics).
Edit: just checked and it's NHBC guides chapter 9.2 and 10.2 - height differences of 0.6m+ must be designed as an engineered solution and have guarding. If you will proceed with the amendment of your garden please check first with the warranty provider about what you intend to do, as it may invalidate your warranty as it would be a modification to the desigh. I couldn't find anythign specific in Building Regs itself, but I didn't look hard once I found the info in NHBC.