I usually turn off animations in most applications and WMs, but they seem to functionally benefit this window management style to help the user orient and recognize where things are relative to each other.

Before Niri I used PaperWM on Gnome with animations disabled and I found that it actually substantially reduces the usability of this sort of workflow for me. I'm not sure how to phrase it, but scrolling WMs feel a little more "physically grounded" and without the animations it was somewhat easy to become briefly disoriented whenever scrolling/opening/resizing/rearranging windows, at least once you start having 4+ workspaces and several screen widths worth of windows on each workspace.

Turning on the animations quickly makes it all snap into place and I never have the brief moment of "feeling lost" after an operation, so it sees inherently important to this WM style. The animations are very fast out of the box and do not feel superfluous.