There are a lot of empty old buildings downtown, too. I don't remember seeing any comparative data in the article beyond that employers seem to be reducing space/employee (they are of course also reducing the number of employees). Of course it makes sense to contract toward the center, that has nothing to do with preferences, it's just economic geography 101.

With respect to the particular building mentioned in the article, it is hardly surprising at all that the NIH is contracting its footprint given recent funding history.

Edit: As mentioned by another commenter, it turns out the NIH didn't move things downtown. Instead, it's just opened a brand new campus that's even further away.