Clarification on HTTP caching (RFC 7234)

Hi all,

I have some questions on the behavior of RFC 7234's s-maxage response
directive -- it looks like the behavior for s-maxage response directive
differs significantly from maxage in that a max-age response directive
means that a stale response calls for "validate", where the behavior is
"validate, but serve stale on a timeout or (if stale-if-error is defined)
on a 5xx".

Meanwhile, s-maxage says " The s-maxage directive also implies the
semantics of the proxy-revalidate response directive."  Well,
proxy-revalidate is the same as must-revalidate, but only operating on
shared caches, and the validation behavior there is "validate or 503 on
timeout".

So the question is: the behavior of s-maxage explicitly to timeout rather
than give a stale response?  I've been looking around the internets, and I
don't see this behavior mentioned in the blogs or even in the O'Reilly Web
Caching book or HTTP The Definitive Guide.

Will.

P.S.  I'm also confused as to what the difference between a "disconnect'
and a "timeout" is -- in one area, a disconnect is referred to as "cannot
reach the origin server" and in the warning it's referred to as
"intentionally disconnected", but there's no direct reference to it.