Note: I did add the web store context to the Context filtering, which is not auto-selected when creating the deployment. From what I see, that's the context under which these customers are created. The script still is not firing.

its far easier to deploy the user event script to all record types and then narrow it down later

Stands to reason that wouldn't fire other User Events then?

the user event execution context is actually the generic execution context when none of the others fit