Found an unrelated bug. (I know, I know, poor form to include this in a thread about a different issue)
When updating an existing legacy UE page with UE4, upon clicking the "Finish" button, all values were updated except for the original "Included" statement which was pointed at the legacy directory structure. So, updates made to the UE4 document weren't reflected in the mail that was sent. I had to manually change the path:
include("../webassist/email/WAUE_ContactColoradoSafety_1.php"); //new path
include("../WA_Universal_Email/WAUE_ContactColoradoSafety_1.php"); //old path I had to manually change from.