Yes, looks that way.
I haven’t tested it, but I don’t think muting will work here anyway since the recipients email address is used in the To header.
But maybe changing the List-Unsubscribe header would be an option?
Currently it (always?) links to Discourse Meta - The Official Support Forum for Discourse which isn’t really helpful if I just want to stop tracking a specific topic.
Feature request: When a mail is sent because I’m watching a topic the List-Unsubscribe header should link directly to (the bottom of) the topic so that I can easily change the tracking state of the topic. When a mail is sent because I’m watching a category the link to the preferences is fine.