Adjust my prior change to better utilize structured form submission...

... to accomodate a plugins that are not using p:config-assignedLabel.

See: JENKINS-25372 for more information.
I found the code, it seems to be a Maven plugin, which means the annotation will block new callers from referencing it at compile time, but not runtime, right?

So this should have zero impact on the jelly callsites this change is looking to accommodate.