Something similar was studied here but not yet approved. It would be the following: within a radius of 150m from home , the height of the highest object within that circle is added to 122m (400ft).
I think it's the same thing you say. In this case under study was the maximum distance that the object that was higher than the Home had to be at, and that distance was 500 feet or 150 meters. I find it very interesting that should be approved here.
Something very curious has happened to me today related to the same thing. I was flying, recording a tractor sowing wheat. A property on a very uneven hillside. The Home in the lower part and the height difference at the top of the property of about 30 meters. Bearing in mind that light aircraft have a 400 foot AGL floor which is the roof of the drones. Flying at an altitude of 105m (350ft) AGL from the Home when I reach the top of the property I am 75m AGL (300ft) but 105m AGL from the Home. A light aircraft has flown just above the drone, which probably flew at 120m AGL altitude (400ft) but too close to the drone. If we add the height of the closest area or object would be more than 120m AGL i would be in airspace of the light aircraft. It was flying slowly and it gave me time to descend without any problems.
But.... do you understand the problem? The base height is calculated from the Home on the drones. In manned civil aviation how is it calculated????????????? I have no way of knowing at what altitude It was flying, maybe lower than allowed, but in the previous case I could be flying higher and all in order, legally, and we would have been on a collision route. It could have resulted in an accident where two people, those flying in the small plane, could have been seriously injured or worse........
There are still a lot of things that aren't clear. Of course, it is preferable to lose the drone than put people in danger, but.....................