Looking at the webpage:

https://matplotlib.org/3.1.1/gallery/statistics/histogram_features.html

It claims that "this demo shows a few optional features:"

Among these is:

"The normed flag, which normalizes bin heights so that the integral of the histogram is 1. The resulting histogram is an approximation of the probability density function."

In fact, it is not shown (density=1 is used instead).

While I'm at it, density is listed as a boolean on

https://matplotlib.org/3.1.1/api/_as_gen/matplotlib.pyplot.hist.html

So it's not clear to me why density=True isn't being used there.