I agree with the conclusion, but am pretty sure that you meant to say s-maxage in that section defining s-maxage. That's all I changed, so it should be fine unless you wanted to add more text to explain why. I don't think it is necessary to explain more because adding s-maxage implies the server wants shared caches to reuse the response.
Restore some 2616 wording on public, must-revalidate, and proxy-revalidate
This ended up being an editorial change between drafts because the only normative changes were already noted for #264 and #268, and this is just rewording what we had for #161.