> I do like evolutionary explanations for a lot of human behavior, but this one feels a little too pat to me.

I agree.

> Patience, "biding our time", "hunkering down", etc. are actual emotional states we can experience and recognize, and depression doesn't feel even remotely like for most people as far as I'm aware.

But I don't think that's a valid counterargument. Depression doesn't need to feel like that or be motivated by that in order to be selected for. As long as it has the same effect as someone actively choosing to reduce consumption, the argument works. (Again, I'm still skeptical of the argument.)

> Also, this explanation would only really work if the entire group entered a dormant depressed state together.

That's valid, though to salvage the argument, you could say it applies to situations where active behavior turns out to be maladaptive. Perhaps fleeing the volcano causes you to inhale more gases and definitely die/fail to reproduce, whereas moping in place gives you a chance to luck out and be in the right place at the right times and thereby survive. That's a stretch, but the other examples are better: maybe the active people compete and kill each other off. Or the active people catch the plague while trying to help out.

Actively avoiding harm might even be the better approach 99% of the time, and yet the 1% where inaction is better means that the trait can survive. Say everyone has an innate x% chance of being active. Event 1: 60% of active people survive, 40% of inactive do. Repeat several times. Event N: the soldiers find and kill 100% of active people and 75% of inactive. The survivors will not have x=100.

Related example: dinosaurs and small mammals. Big things did really well until they didn't.