This article from the Washington Post gauged black support for Massachussetts Democratic Senator Elizabeth Warren and Vermont Independent Senator Bernie Sanders based off of looking at the composition of a few campaign stops.
Perhaps the reporters felt this is fair because they compiled some stops, but the plural of anecdote is not data.
The polling shows Sanders is getting more African American support than California Democratic Senator Kamala Harris, who the article seems to posit as having some sort of advantage with this voting population.
One of the problems with the media is it doesn’t practice a lot of rigor when it comes to reporting and analysis, it bases far too much of its information on personal biases and anecdotes rather than comprehensive surveys and research. This is a long time problem, but the media could always get better.