I find it ridiculous that one part of Chrome is forcing me to add user agent sniffing while another part is trying to deprecate it. They need to get their act together: their decisions have massive consequences across the ecosystem and they need to be more responsible.
Perhaps you can correct me on why that's not so.
And I think the chrome team could have come up with a solution that didn't involve browser sniffing, such as sending a header in the request identifying that SameSite=Lax is the defualt, or that SameSite=None is accepted. But instead they recommended sniffing the user-agent string.
So this means that if you need to use SameSite=None you cannot without UA sniffing, which I think is what the parent was complaining about.