Sorry, but that sounds like absolute crap to me. I have never known Apple to diss one of their products, particularly a new one.
Now of course, if you are talking about the higher rated 'ac' spec communication protocol, then that may be correct, as most older devices cannot achieve those speeds. As new updated models are released, that will change.
Communication will occur at the speed of the other device, whether at the original 'a' or recent 'n' rating or whatever.
Overall, though, the new version provides better signal strength, better distances and faultless performance.
I told a lie earlier, when I said that I bought the ordinary Extreme. I too got a 2Tb version to allow for the MBP's in our house to be 'Time Machine'd. Specs are otherwise the same though.