Incorrect. Not required is not required. You do not need to supply rationale or get agreement by anyone else that your reasons are good in their opinion and not just in your opinion.
Should just means the thing is preferred. It's something that is good and useful and helpful to do.
That is not "must unless you can convince me that you should be excused".
“ SHOULD This word, or the adjective "RECOMMENDED", mean that there
may exist valid reasons in particular circumstances to ignore a
particular item, but the full implications must be understood and
carefully weighed before choosing a different course.”
I don't know if you thought you were validating or invalidating my argument, but this says exactly what I said.
Further, not only the presense of the words "should" and the doubling down with "recommended", also the absense of the words "must" or "required" or "shall" is pointed.
Because those words are used elsewhere. When something is actually required, those words are used, and so when they are not used, it is meaningful. It means no one is free to put their own words into the authors mouths and say "well they didn't say it but obviously they pretty much meant required" when they so pointedly chose not to say required.
And it's not a technicality. A thing either is or is not required. There are no other states. The spec does not require it, and so for Google to require it, Google is not adhering to the spec.
Since the spec does not require it, you can't say either that it falls under "full implications". "full implications" cannot include "Some servers might require it", because that would be circular logic. No server can require it in the first place.
