[foota]

Browsers are free to make a request "just in case" with cache control. With immutable, they are strongly discouraged from doing so. My point is, browsers aren't broken according to the spec if they make those just in case requests.

[manigandham]

That is 100% on the browser to optimize itself. Otherwise it's diluting the point of the existing cache header if we need to add a flag to say "we're actually really sure about this expiration time"