Pom, what is the origin of this definition?
Can we assume a SOTA station on a summit being a temporarily fixed station as you cited here. And does BNetzA have the same understanding?
When looking from a different angle: The army is the primary user on this band. If amateur radio causes interference, they want to know where the interfering station is located (and probably shut it down). This would be rather difficult with temporarily fixed stations.
I would be more than happy to activate on 6 metres but my guts feeling says “No!”
73, Roman