Sum of weights (squared) in WeightedMean histograms not filled properly

[olbessid]

I am filling histograms with storage type WeightedMean. I then want to retrieve the sum of weights and more particularly the sum of weights squared bin by bin. But I find that calling both these properties just returns the number of histogram entries. I am using python 3.8.
Attaching a minimalistic example to illustrate the issue. I wasn't able to attach the notebook itself, so I made a screenshot and also collected the code in a pdf.

notebook snippet.pdf