I am really not surprised, Jacob... It is hardly unusual for things like tiles and even dishes to have high level of radioactivity... there is the famous example of the radioactive yellow glaze on a batch of mexican clayware...

Now think how sensitive those detectors carried by the NEST team are...They are made to find radioactivity that is TRYING to be hidden by shielding... so the "natural" unshielded tiles set them off
next the seals come on with milder detectors and find not much...

It is just a case of caution being exercised at the first indication of a possible threat... I think it was handled well... I for one have no plans to try to fool NEST teams... I bet the equipment they have is cutting edge.... It may over react but that is better than the alternative!