What you're calling de-gentrification isn't really the opposite of gentrification. Gentrification is the destruction of long-standing neighborhoods and the displacement of poor people, who may have no good place to go and lose their support structures. Often, those poor people rent their homes/apartments, and so they don't benefit from the increase in prices. Their rent just goes up until they have to leave.

Rich people fleeing doesn't bring them back. Whatever they suffered in displacement is just sunk. In the very long term it may form part of a new cycle of gentrification, but only after the neighborhood has lost a lot of its old value and is usually accompanied by the kinds of desperation that poverty causes.

So it's not a good thing -- though you're right that this study is so dubious that it may not even really be an issue.