I think he's running into the issue that when the phone is playing loud audio through the speakers, it has trouble picking up voice over that. iPhones don't have the same audio separation hardware as HomePods.
Yes, this is why my initial comment was a bit snarky. GP wants his phone to have properties it fundamentally cannot have, and is not expecting that of any other phone.
I tried it several times. It worked 4 out of 5 times on the phone. You know what it doesn't do?
It doesn't stop the timer on my Apple Watch, which keeps buzzing even after my phone stops. The Watch stops if I press the button,
I couldn't get the Music to work.
So, can we be done? I have a couple of Amazon Echos. They just work as a hands-free voice activated device.