I Read part of this as "Is Matthias lying". And although we've never spoke directly, I thought "What an absurd proposition".
It likely makes sense for things to be Note when mastodon wants to read them. I Wonder if there is a possibility of content negotiation, so that when mastodon asks (presumably with mastodon user-agent) it gets a note, but future improved software could have a different type.
It's an interesting problem, as you can never truly own all clients