Partial Configuration File Naming

In part 4 of the DSC Book, there is a section about partial configurations file naming details.
It says that in WMF 5.0 asking for partial configuration “Bob” would make pull server look for “bob.mof”
And that because of Azure Automation, which stores partials as “PartialName.NodeName.mof” it has been changed in WMF 5.1.

I cannot make ma pull server work that way. $PSVersionTable.PSVersion on the pull server says that it’s 5.1,
but if I setup LCM for a host X to include partial named “bob” and place Bob.X.mof (and its checksum of course)
on pull server I get:

“Executing Get-Action on partial configuration ‘Bob’ Failed. Please ensure the parital configuration and its checksum exist on the server.”

It works either when I put Bob.mof on a server or when I configure partial named Bob.X in LCM mof.

Am I misunderstanding something?