Major Using the workflow plugin, the checkout step using PerforceScm does not provide any parameters for syncing to a particular changelist (or label, etc), and instead always syncs to head.
The workaround of manually running p4 sync has several drawbacks, including not appropriately setting Jenkin's knowledge of the changes being synced to.
As per comment below retitling as documentation task.
[JENKINS-28301] Update P4 Documentation regarding Pin parameter
A C
added a comment - Ah ok, yes please update the docs with this info, I was confused as to what "pin" was since it's not in my normal p4 lexicon. Pin does appear to do what I want.
A C
added a comment - Ah ok, yes please update the docs with this info, I was confused as to what "pin" was since it's not in my normal p4 lexicon. Pin does appear to do what I want. 
Paul Allen
added a comment - Documents updated...
https://github.com/jenkinsci/p4-plugin#building-at-a-change 
There are a few ways to do this.
1. Set Change or Label using Build Review (see docs on GitHub)
2. Use the pin at label/change to fix a Job to a point in time.
3. Use the incremental option.
For points 2 and 3, I do need to update the docs when I get a free moment.