I quickly looked & they I think they dont say that at all
I dont think they even mention T2x TAA, do they?
They mention smaa t2x though perhaps youre getting confused.
The general rule = with the same method the higher the samples the better the quality but at slower performance
In this case it may be a bit different.
From what I gathered SMAA 1tx used in Ryse uses several previous frames blended in the same single (1tx) temporal AA buffer. So the temporal component is more robust (no more temporal artefacts like ghosting seen occasionaly in Infamous) but at the price of some constant blurring (and indeed Ryse is a lot more blurry than the usual 900p->1080p upscaling typical blur).
When SMAA 2tx uses 2 previous temporal frames stored in 2 temporal buffers (2tx) and the algorithm chooses the best previous samples (kinda) depending of the scene.
But I suspect the temporal AA component might/will have many implementations and/or combinations.