Actually now that I look at the graphs again it is labelled as NRC Reference. So it looks like both graphs were taken at the NRC chamber but use different scaling like I noted above.

And JohnK is correct. Anechoic chambers don't measure accurately below 100hz including the NRC's. That's not to say it won't show bass extension like when comparing a bookshelf to tower in this case. It's not going to be completely accurate though.

This is why when you measure subwoofers you do it outside and not in a anechoic chamber

I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne