A flat ridge or displaced ridge in the NAO region won't slow down the flow. Rather it will suppress the flow (sliders) but allow things to keep zipping along quickly. Also the ridging keeps rolling over and a true block never establishes, tho some will argue semantics over what a true block is. We are seeing short-lived blocking but overall it is flat ridging that continually rolls over on itself keeping the flow underneath flat and fast in the NS.
I'm not saying the GFS is right, but that is not the look verbatim of a blocking regime in the NAO region nor is it a big dog look.