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Google began pushing for it to become an Internet standard—explicitly to be applicable to any URI-driven Internet system, not just the Web—in 2019, and it was adopted as an Internet standard in 2022.

https://developers.google.com/search/blog/2019/07/rep-id

This is true but irrelevant to the parent's question -- in the article, it's made clear that Google's requests are happening over HTTP, which is the most obvious reason why robots.txt should be respected.

It's relevant because it attacks the premise of their objection.

Read the OP; it's obvious based on the references to robots.txt, the User-Agent header, returning a 429 response, etc, that most (all?) of Google's requests are doing git clones over http(s).

Because it uses HTTP.