What he's doing is something else
audio notes are different from transcriptions of notes.
Discussion
Yes but that's where he's tricking you. It's not just the transcript. The audio is a completely different NIP and event kind breaking interoperability.
I haven't read any nip and I don't know what event type it's using. I don't have an iOS device.
Even for calls, I don't think Voistr and Noscall are interoperable.