The simulation is, rather obviously, what's being referred to with the spiral-of-death -- it's not unusual for instance in Age of Empires II to encounter transient periods where-in steps take an order of magnitude or more than the period they're simulating on less-capable machines (due to some O(n*n)'s in the AI system).

In the end this is still a decision regarding how to handle player's falling behind; too far and they're effectively taken out of the game as they're no longer interacting within a sufficient approximation of the current state.

Under what design is "high ping" going to cause the game to run at lower "speed"? The only possibility I can see is where-in the turn period is, for some bizarre reason, also the granularity of the simulation step and you're also adapting the turn based on player latency (in aid of fairness, usually)

Having implemented such a system myself, a few times now, it has in practice performed sufficiently well.

DE is garbage in general so it's not really a fair comparison.