In a highly liquid commodity market full of professional traders, I'd agree. But the housing market isn't that liquid over 9 months and there are a lot of small timers. It seems more likely there'd be some sort of initial wobble as sophisticated participants reposition, then a period of calm, then the actual impacts set in over a few years.
It might not happen that way - someone does need to check - but at 9 months I wouldn't read much in to this study. The physical market would still be reorganising and it seems entirely possible that the eventual impacts are just different than what this study suggests. I'd want a period of more like 5 years to be confident that the data had given everyone in the market enough time to feel the impacts of artificially low rents and reposition appropriately.