Citi ThankYou Points Expiration After Product Change

What has been your experience with expiring ThankYou points after doing a product change of a Citi credit card? I recently converted my Double Cash to a Custom Cash, expecting the ThankYou points to transfer over. Fortunately, I looked at my points summary on ThankYou.com recently and saw that some of my points had an expiration date. Upon closer examination, the Double Cash was deemed "closed," so the expiration clock had allegedly started.

Is this normal? According to other data points on the web, product changes to a ThankYou point-earning card was supposed to prevent expiration of the previous card's points. Please let me know what your experience has been