parallelCollectionScan does not work with mongos, but this limitation isn't documented

The parallelCollectionScan command does not work over mongos.

This is mentioned in passing on the Java driver Getting Started page (http://docs.mongodb.org/ecosystem/tutorial/getting-started-with-java-driver/#parallelscan), specifically here:

ParallelScan does not work via mongos.

It is also mentioned on Google Groups here:

https://groups.google.com/forum/#!topic/mongodb-user/Ss-uhnUbUbU

However, this limitation is not documented on the page for the parallelCollectionScan command itself (http://docs.mongodb.org/manual/reference/command/parallelCollectionScan/)