I had/have a Pixel 6 and it sounds like it didn't have MTE. I kept it for the 5 years it would receive updates and in about a month it gets no more updates GrapheneOS or otherwise, so I bought an 11. And now there will be no GrapheneOS for it because it doesn't have MTE?
I can understand it may have been a good security feature for whatever Pixels had it in between, but if it was not so critical that its absence forced you to stop producing builds for the 6 I don't see why it precludes you from doing it for the 11. Especially when it sounds like from all else you said GrapheneOS on an 11 would be more secure than what I had on a 6 and I fail to see how that's not a positive for someone like me upgrading from a non-MTE version to another non-MTE version.
You could still argue you don't recommend it over the 10 because it lacks MTE in spite of other enhancements, or try to educate people on the trade offs between MTE, Titan M3, and other features, however I struggle to see that the argument of GrapheneOS on Pixels being dead purely over MTE makes much sense given its absence on other supported models. Doubly so when there are only vague 2027/2028 dates being given for a Motorola release.