Maybe dad didn't give permission to record or air it. Someone else mentioned that they can't record a call without permission so the grandfather call was probably a reenactment. I suspect grandpa isn't exactly a master thespian. He already knew and most likely had some time to process the information. Given Sean's situation, his family has probably been prepared for this for a while now. Your average person probably isn't going to sound especially emotional in recreating such a phone call.
My mom informed me of her sister's death last year via a text the morning after she died. We had all been there the day before (she did not appear to be aware of our presence, but who knows?), and she passed in the middle of the night, after everyone had gone home, or gone to sleep. We were expecting it, and in some ways it was a relief, because she had been suffering for a long time. So I was sad, but I didn't break down crying or anything. If I had to later reenact the moment I found out for a TV show...you probably wouldn't think much of my reaction.
(We’ve had a couple of unexpected deaths in the family in the past couple years and my mom would never have texted me about those. The first one was my cousin, and my dad told me and my mom together in person; the other was his brother's ex-wife, and my parents called me and told me over the phone. Just so no one thinks my parents would normally convey such news via text.)