[davidben]

Ultimately we can't do anything about a server that is near-maliciously determined to be wrong. The hope is we can at least defend against some of the common genuine mistakes at fairly low cost.

The implementer that tries to special-case GREASE values must have first hit an interop problem and thus had a second or third opportunity to think about it. I would hope, at that point, they realize they're meant to ignore unknown ones!