What you get is correct because in your case the histogram minimum value is negative. Negative content in an histogram means it as been filled with negative weights. In a such case bins with 0 content may have been filled (sum of weight being 0). Do not set the minimum to -1 and you will get the expected behavior.
I want to plot the difference of two histos which naturally can be negative (hence I need the minimum to be smaller 0). In my case a difference of zero will never occur (as both numbers are float). I.E. there are situations where “wrong/dangerous” plots are practical
Since there are the two drawing options P and P0 why not using them . At the moment for histos with Minimum < 0 P and P0 are identic…