Dear respected Douglas M1,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
As per your description, yes, I'm sorry and I'm afraid to say that the Rehearse with Coach features don't work in presenter view.
We feel your pain due to this limitation and we’re really feel sorry for it. Regarding to your concern, to make a future suggestion about improving PowerPoint, I request you, please send/provided feedback to related PowerPoint development team via Microsoft PowerPoint feedback portal (select Windows OS platform and click on Send feedback button), Submitting sends your suggestion to the PowerPoint programming team so that they can get notice about it.

We can expect this feature to be used in the future in PowerPoint app.
Appreciate your patience and understanding and thank you for your time and cooperation.
Sincerely,
Waqas Muhammad