Well I was wondering this either.
It might also be possible that we never enter line 7050, where we set pixels to be COL_PURPLE.
I'll do some quick observations.
In either case, "too slow" will be marked on the station graph.
Oh well, I hadn't expected this tbh.
Thus it might be possible that "too slow" passengers recorded at the stop never actually attempted to use the stop because they always prefer the car anyway?
Doesn't sound meaningful to me in the first place. I'll put some thought on what these stats should record imho.