I would argue that while it _feels_ wasteful to us humans, as we perceive it as a "big recomputation of the rendered graphics", technically it's not.

the redrawing of anything that changes in your ui requires gpu computation anyway, and some simple blur is quite efficient to add. Likely less expensive than any kind of animations of dom objects thar aren't optimized as gpu layers.

additionally, seeing how nowadays the most simple sites tend to load 1+ mb of JS and trackers galore, all eating at your cpu ressources, Id put that bit of blur for aesthetics very far down on the "wasteful" list