How does call assist feature work?

One of the features of iOS 26 is supposed to be call assist or hold assist. I recently placed a call and had to wait on hold for a few minutes. I tried the call hold feature and it showed it would notify me when it was time to pick up.

i was holding the phone the entire time. No visual or audible indicator when it was time to pick up. Instead what I saw was a notification that yr party I called hung up.

Had to call back again and this time wait on hold until the call was answered. So, how exactly is this feature supposed to work?