I agree with you.  The desirable solution is to have that built into the app layer.

The reason I did this as an app config is to give us an option to turn when things are going south.  Picture if you will, a cluster in overloaded meltdown, it's the middle of the night and the app team is nowhere to be found.   You have a very tired syseng on the line with you who needs to get back operational.  With this setting you can slow up the request rate to riak.

You don't have to enable it.  And it only fires when things are bad.