dddd

As I mentioned earlier, the cage on a 1x system can be shorter by virtue of not having to handle the chainring changes. Also, this arrives in the era of no more 26" wheels/tires being fitted to race-quality bikes, so ground clearance was already made less of a concern.

Further, as the largest cogs are selected, the lower end of the cage has already been pulled well upward/forward, this presumably being when the most technical riding might be expected to be encountered. Also the "B" or mounting pivot doesn't move at all, which eliminates some of the wild swinging in all directions of the cage pivot, something I would expect to somewhat improve ground clearance at speed.
On other other hand though, any upward impact to the lower end of the cage while it is pointing relatively rearward would tend to dramatically increase chain tension, since the "B" pivot on these derailers is fixed-position (i.e., not sprung), which might have the derailer snapping free of it's mounting bolt if not outright snapping into large pieces(!). So methinks that a sprung or sacrificial element at the B-pivot adjuster is warranted, even if such a sprung device were heavily pre-loaded against a stop so as not to move at all in normal operation.

It occurs to me also that these 1x derailers might optimally swing the cage along an additional axis, over and above the motion axis, however virtual, that common parallelograms move around. Since there are no chainring changes to consequentially alter the indexing at the rear, the cage can now be made to angle inward and outward as needed to best effect running clearance at the bottom (where the chain is being fed onto the teeth) between the chain and the next-larger cog, while shifting across the stack of dished sprockets. Eliminating any chainring shifts really frees up the rear derailer design to work best in terms of shifting across the cassette, and I expect this new derailer will fully exploit that design freedom.