Is Pixel 4a really not recognized by Xfinity unless it's a 5G??

The IMEI on my new Google Pixel 4a is not recognized by Xfinity and customer service also said so. However, the phone "thinks" it has been activated and I am able to use it in every possible way. I am concerned if I am overlooking some issue that may crop up, for example when a bank attempts to send an authentication code directly to the phone on an authenticating app.  If I have to return the phone I need to do so soon.