It's not so much the peak speed as the overall capacity. Verizon and T-mobile don't have the ability to put 150+ speeds all over the nation, because they don't have the spectrum to do so.
Sprint by contrast has enough 2.5ghz spectrum to deploy at least 3 carriers all over the nation. If/when they get 3 carrier aggregation up and running, that's a solid 180+ of peak speed. Additionally, they have more than enough spectrum in most places to keep adding additional carriers once things start to get filled up.
Now having the spectrum and having it deployed are two different things. The article is saying that the potential for speed/capacity that sprint has is disturbing to their rivals, as it should be. We will have to wait and see if they are able to use that potential.