Is it a materialized remapping of the underlying .hgt or is it done client-side, in some webGL-shader? (if we'd even need that, plain js or wasm might be good enough these days?) I could imagine this being even more compelling if we could interactively shift the remapping to put regions we are currently interested in into high saturation parts (and/or scaling it down to make mountain ranges "readable").
Another, even simpler reading help would be sampling the color at the mouse position and displaying a translation into meters.
In any case, the vertical perception amplification (compared to other visualisations) is truly awesome! in my region I can easily make out the forest offsets that SRTM and LIDAR data happens to come with, and bigger roads cutting through those forests.