Currently Sizing 3 defines intrinsic sizes of replaced elements explicitly.
This definition isn't correct, and it should be deleted in favor of falling through to the CSS2.1 reference used for non-replaced elements.

Agenda+ to point out that the implication here is that, when an aspect ratio is present, min-content and max-content are dependent on sizing constraints in the opposite axis. (This might be surprising/disturbing to implementers but is probably as expected for authors.)

I really don't want min-content and max-content to be anything other than intrinsic sizes. And, in particular, I want them never to depend on the element's own specified sizes, precisely so that they can be used as keywords for the element's specified sizes.

Doing so could cause problems down the road if we ever add the ability for calc() expressions to reference concepts like "this element's min-content size in the other dimension" or "the grandparent element's size". (The latter is harder than the former, but we might be able to come up with a set of ways where it does make sense or a way of resolving the constraints, and having things like "intrinsic" sizes that are almost but not quite always intrinsic would make that harder.)

The problem with that is then we don't have a keyword for "shrinkwrap this thing as if it was a float with (infinite/minimal space)", which is what you generally want in e.g. grid track sizing.