I guess you suffer from the problem that PDFs are densities, but histograms display counts, i.e. your histograms needs to be normalised using the bin width.
I remember that somebody asked for this, so I proposed some code in this post
to normalise the data by bin width. Could you try if this gives the expected result? If yes, I can make this option more easily available when plotting a histogram.
The plotting code also looks like the results might differ based on the data error that you request (see the first post you linked to). I never got a reply, so could you check if this makes a difference?
It seems logical to me, because Poisson errors cannot be computed for non-integer quantities. Therefore, when you scale bins, you need a different error model.