They don't look propped at all in the photos. Also I think propping would be hard for the cleaning robot as it looks like is a super simple little robot with small wheels and just rolls straightened over them.

Yah its probably a case that designing a vacmop style device (possibly purchased off the open market?) and having it drive around on a flat surface is both cheaper and keeps the panels cleaner than a custom bot that doesn't clean as frequently because it costs to much.

My question is whether sitting on the ground itself causes problems with efficiency due to the panels getting hotter than they would with some airflow under them.

According to the research on their site, ground mount solar has better heat dissipation than roof mount solar, and isn't that far behind racked systems, so it's not really a concern. The ground ends up acting as a heat sink.

https://www.erthos.com/modeling-heat-dissipation-in-earth-mo...

Erthos spend quite a bit of time designing their own autonomous cleaning and repair robot.

All panels collect dust, but this setup is much more challenging to clean (and to generally service, i.e to replace a faulty panel)

They have a robot that cleans the panels. It's a big, flat surface so they don't really need anything much more advanced than a Roomba.

Apparently they also have special shoes that maintenance people can wear that distribute the weight properly so they can walk on them if they have to.

This seems much easier to clean? A gigantic flat slab is pretty easy to automate something vs disconnected racks.

(Modern utility scale PV installations are already using automated cleaning solutions).

It is much better from POV of the cleaning robot maneuvering requirements. It's also much better in terms of single robot can access the entire installation.

But it's worse in terms of how much distance the dust should be pushed before it's off panel (as I don't see any gaps there)

Alternatively if the robot is a vacuum or something of the like, it could just store the excess dust and dump it at a station on the edge.

Service trade-off seems pretty marginal. They say the panels aren't tied down to the ground in any way, so you might be able to just pick one up and disconnect it