FWIW, I am pretty sure I agree with you/OTR, but the IETF Messaging Layer Security (MLS) people disagree for not-always-trivially-dismissible reasons (indirect link because I am lazy).
The problem isn't any one individual who is/isn't involved, it's the consensus mechanism. If you bring in a great sous chef and ask them to make you an omelet, they will make a great omelet. If you bring in a committee of people -- some sell omelet pans, some run hotel chains where free omelets are part of the package, some want you to adopt their vegan egg substitute -- you are not going to get a great omelet spec. Adding one omelet expert to the committee doesn't add anything over just asking an omelet expert to make some eggs.
They would absolutely not love to have me, and I keep away from their mailing lists as much as a favor to them as to my own sanity. I'm not alone in the wilderness on this opinion that IETF process produces abysmal cryptography, by the way; Bernstein beat me here by 2 decades.
https://news.ycombinator.com/item?id=25101825