We discussed this in Thursday Stan general meeting. We’ll make fixes for the next RStan release, and the release after that is likely to be using posterior package.
PR has been merged
Thanks for addressing this–much appreciated! And sorry to be slow to respond (start of the semester). By PR you mean the public release of the development version of rstan?
The pull request was merged to master branch, and I think it has been submitted to CRAN but is not yet there.