Is click-through rate (CTR) recorded for promotions?
Yes, the click-through rate (CTR) is recorded for promotions, even if the promoted result is not in the index.
That allows you to record interactions with promotions that point to other sites. Whether that is a product from a partner or simply a URL that is not indexed.
For example, if you have a web app with a login screen under
app.webapp.com/login you can promote that URL when somebody searches for the term login on your site
webapp.com, even though the subdomain
app.webapp.com is not being indexed.
Ensure click tracking is enabled to ensure CTR data is recorded for your search implementation.