Documentation search does not include all relevant results

I was looking at documentation for changing color of the fill based on whether it is above or below 0 and I found this example https://www.chartjs.org/docs/latest/samples/line/segments.html which has "segment" field in it that does it for the line(not for the fill). But when I go to documentation, to see if it supports fill, https://www.chartjs.org/docs/latest/general/data-structures.html there is no mention of this property(and others from the example). In the API documentation(which is utterly useless) there is https://www.chartjs.org/docs/latest/api/interfaces/Segment.html but has no properties from the example whatsoever. In other words, I find the documentation quite useless.