I understood it as in, whatever speed you start with, keep the same pace throughout the technique.
I dislike being asked to attack slowly, and then suddenly being thrown fast.
I dislike that, too - and - if you get part way through the ukemi (just before kime) the sensei pauses to make a point and then switches from slow demo to fast demo... Grrrr. ("Here, you want to get him stretched out like this where he's really light (as Walter manages to keep his 100 kg from falling when the movement stops, and teeters on the edge of falling) and then you finish off low and fast like THIS." (oops, gotta accelerate the 100 kg back up to speed for the big over-the-top ukemi for kotegaeshi)) Should be able to deal with it, but that's the wrist with the old injury to one of the carpals...
Speed... Full speed practice is important sometimes if only to learn that what's more important is timing and ma-ai.