Thanks for the link.
The observation that the resources used for an immune response are
dosed for an optimal performance sure makes evolutionary sense. However, saying that evidence "suggests that the immune system has an on-off switch controlled by the mind" is dead obvious, with or without detailed models of the reasons why organisms would work like that. The big question of
how does that switch work, as you suggest.
The headline, "Evolution could explain the placebo effect", as usual with press releases, is far-fetched. Evolution can explain why that type of response is a good strategy, but explaining the mechanism itself is another story.
"The Menu is Not The Meal." - Alan Watts