TL;DR;
– in a cluster –
mongodump --host `hostname`
does not pull data from *hostname, as documentation would suggest.
*pulls from multiple systems over network – unexpected

In testing out some things for performance, we noticed that mongdump was not pulling its data from the local system, and was instead pulling it from the primary, even though documentation suggests that passing the --host flag with the local machine would default to "nearest"... which of course, would be itself.

It does appear to be pulling from multiple systems at once. However, it would be significantly faster in our network design for this particular system to avoid going outside of itself for backups.

Since documentation suggests that we're getting results we shouldn't, I'm filing this as a bug vs a feature request.