If the ore sorting plant is full, excavators with materials in their buckets with the status "WaitingForTruck, Stopped" will still consume fuel (at a reduced rate). In the attached screenshots you can see that it's been multiple months, the excavator hasn't moved and is still consuming fuel. It's not specific for hydrogen mega excavators - I recall noticing the same thing with normal Diesel Excavators a while ago. Meanwhile, trucks that are loaded with material that are waiting for the sorting plant do not consume fuel.
Oops saw that I missed the fuel consumption on the first screenshot. Here's another one (still drawing fuel 🙂 )
