Because none of the things said actually refute any of the points in the Google discussion? At all?
I also definitely don't feel a failure to go off and survey every random library that exists for rust makes a discussion "woefully incomplete" or that it isn't debating rust at it's strongest. The same treatment is given to all languages, including rust, go, etc.
The discussion is also about language features, and it discusses the language features.
How does it not? It seems to me that OP revealed an alternative method of error handling (which is very cool I might add), exactly in response to Google's discussion on Rust's error handling.
If the discussion doesn't address this, then it seems reasonable to say it's incomplete, as its omission makes it appear they're not debating Rust at its strongest.
edit: paper->discussion