Yes, I’m really watching the exact number of safe days (37+), but I liked the YBR-nostalgia of watching/being in lanes.
Indeed, my guess was that this was an aesthetic issue. It’s clear to see how the degenerate case, where only part of a single yellow line, or none at all could be confusing. I’d say shading could be accomplished by actually shading in a light yellow, with darker lines overlaid.
In practice, one could say that currently every goal’s good side is marked by a different “shade” of yellow. I’m talking about the emergent shade (caused by the density of yellow lines) that’s especially apparent when looking at the graphs in thumbnail form. Maybe some people are depending on that shade to get some kind of intuition about the intensity/slope of the goal (flat forever goals tend to be really yellow) or maybe the gallery would look bland with only a single shade of yellow? But maybe it’s something to consider experimenting with? Maybe a unified yellow shade results in a cleaner and less noisy design feel?