It's not the shell that produces random walks, it's the larva of a moth living inside the bean. The larva cannot see the environment, it can sense the temperature, so jumping in a random direction is a means (or a strategy) of the larva with the goal of achieving optimal temperature. It works well in their environment, because the temperature rises if they are exposed to direct sunlight, and a few jumps in a random direction might just get them to shade to a lower temperature. In the shade, they stop jumping.

"Strategy" makes clear sense for humans. A group of people could think some problem through and adopt a strategy to solve it. For any other life we know of, it quickly stops being meaningful. We may sometimes say that cats or dogs or chimpanzees adopt strategies, because we often like to talk about them as agents. But as we move towards less complex/intelligent forms of life, it quickly becomes clear that we're only ever dealing with biased dice throws.

Point being, I wouldn't worry too much about "having a strategy" vs. "natural selection selecting for". It's only ever the latter - perhaps with exception of humans, but that's up to philosophers to figure out.

I think that's right. I don't think the article is imputing "strategic thinking" to the individual larvae. They carry out a strategy, but they probably didn't whiteboard it themselves.

I thin it's mainly the ability to start or stop jumping according to temperature. Jumping in a random direction, only when you're too hot, is a strategy for finding shade. Given a pattern of light and shade, that strategy is provably better than never jumping at all, or jumping regardless of temperature.

I think they're saying a jumping bean "has a strategy" in the same sense that a Roomba "has a strategy."