Do you suggest there is any security benefit of a short canary? Or is it just about keeping a canary simple and comprehensible even for non-technical users?
You haven't provided any argument to rebut, only an assertion.
On the surface, there appears to be no actual canary-specific value to keeping the text short. If you have a specific reason you disagree, feel free to bring that argument forward.
rsync.net and rsync the open source project aren't related, afaik/afict. At the very least, no one at rsync.net has been the maintainer or original dev of rsync. Rsync either doesnt enforce their trademark, or rsync.net has an agreement with the project.