Disclaimer: I didn't read more than the first page of the paper

But there are lots of possibilities, right? For instance, if the alternative is glia starvation, and the myelin can be later regenerated, that might be preferable to glial death.

Separately, it's been theorized that myelin first evolved as an energy storage. It may respond to the same biological processes that cause adipose tissue to release fatty acids.

Further disclaimer: I don't really know what I'm talking about, but it seems like there are lots of possibilities why this observed result might have an evolutionary purpose, or explanation.