I think you're indirectly agreeing with the parent (and great-grandparent); both are saying "Google (and others) shouldn't just use the IP; use the browser's language setting, and if that hasn't been set, the OS setting", which you also seem to be agreeing with.
The only one differing is the grandparent, which was asserting first that users might think showing anything other than the local language is an error, and then asserting that users want their native language, and so I'm not really certain what they're asserting since those two are not always the same (maybe that the first is the reason Google does it, the second is asserting the preferred behavior, which is nearly agreement, in that the latter is doable via OS or browser preferences).
The only one differing is the grandparent, which was asserting first that users might think showing anything other than the local language is an error, and then asserting that users want their native language, and so I'm not really certain what they're asserting since those two are not always the same (maybe that the first is the reason Google does it, the second is asserting the preferred behavior, which is nearly agreement, in that the latter is doable via OS or browser preferences).