My question is about: https://www.mnot.net/blog/2007/05/15/expires_max-age
The problem with that line of reasoning is that HTTP versions aren’t black and white like this; just because something advertises itself as HTTP/1.0, doesn’t mean it doesn’t understand HTTP/1.1 (see RFC2145 for more).
But here they are saying:
If a response includes both an Expires header and a max-age directive, the max-age directive overrides the Expires header, even if the Expires header is more restrictive. This rule allows an origin server to provide, for a given response, a longer expiration time to an HTTP/1.1 (or later) cache than to an HTTP/1.0 cache.
So or the article is incorrect, or W3 is incorrect (or I'm wrong :p). With the last sentence, W3 means you can give a different expiration time to a HTTP/1.1 cache (or later), compared with a HTTP/1.0 cache. You can do this by using max-age and the Expires header.
So they can only say something like that, by assuming the HTTP/1.0 cache will ignore the max-age, because otherwise you will just have the same expiration time for all the caches (HTTP/1.0 and HTTP/1.1 et cetera).
So what is true about HTTP/1.0 caches understanding max-age?