"Interaction" != work
Yes, open plan offices make it less likely that people will chat to each other. Not only are they doing so in plain sight of everyone else - including the boss, but they are much more likely to be politely asked to STFU by all the surrounding people trying to get on with their work.
But the research sabotages its entire credibility with conclusion:
> The second is that we just don’t know all that much about how humans interact,
So it turns out the researchers were measuring something they didn't understand. It therefore follows that nothing they "discovered" has any real significance, since it was based on a badly designed experiment.