Hi Evan.
Thanks for your bug report. This is a known issue with Docker for Mac.
The [f]stat[v]fs family of functions is not yet supported by the Docker for Mac file-sharing solution, osxfs. We have plans to implement the necessary functionality to support both querying file system metadata and sharing the OS X mount table with bind-mounting containers. This support should arrive within the next 2 to 3 weeks so keep watching the changelog, updating your installation, and trying again once more mount point support lands!
In the meantime, I’ll add your use case to our compatibility test suite to ensure that, once we can support it, we do not regress support.
Thanks for your participation in the beta programme and helping to make Docker for Mac more awesome!
– Dave