Plotting offset errorbars with pyplot.errorbar()

We use errorbar() to show the expected range of a probability distribution with an associated observed quantity. Sometimes, the observed quantity falls outside this expected range, which we were able to plot by specifying negative xerr values. An example of this can be seen here.

After reading this issue and the documentation, it seems this is not the intended use-case for errorbar. I have a couple of questions. First is purely out of curiosity, was there any reason other than the < 3.6.0 documentation suggesting that xerr and yerr should be positive values that it was changed? And second, what is best way to recreate this image without essentially rewriting the errorbar function to plot the lines and caps independent of the scatter plot. Possible follow up, if the only reason is to be consistent with the documentation, would you accept a PR from me to revert this change and update the documentation accordingly?