Nowhere, but he also makes it sound like you run one blockstring until your pressure runs out, which, frankly, is not a way I've ever heard anyone discuss blockstrings.
So I made a distinction where a blockstring ender is something you can't or don't chain anything else off of (example, Tsubaki 6B), and a pressure ender is something you can't or don't chain anything off of that also doesn't allow you to continue pressuring (like what he states Ragna 2D is).
Pressure enders would be a subset of blockstring enders.