My "bad", didn't select the churn template under the Retention group when setting up the model. But question, if I miss this in future, shouldn't I be able to change the template by clicking Settings on the upper right of any page in the model development process? I tried that first by changing Category Labels for Predicted and Alternative Outcome, but it didn't seem to work (saved, refreshed). Was easier to just delete and re-create the model.

You are right, once a template is selected and a project is created on it there is no way to change the template. But as you have already figured out, a template is only vocabulary for the project, you can change the vocabulary from setting and if you wish use the new vocabulary as a new template.