[enhancement] Specify behavior in the form of Valid Behavior lists

For the most part I like Valid Usage sentences (they could use some thematic organization though, and some other QoL tweaks; I have some ideas there too). The good part is they incentivize the text author to form the requirement in atomic, complete, formal, structured, and normatively forceful (i.e. "must" sentence) manner. While free text incentivizes more colloquial descriptions that also convolute multiple aspects together.

So I wonder if there should equally be Valid Behavior lists, which would analogically enumerate the requirements of the implementation. For commands that return some struct, it would be virtually same as VUs, describing the restrictions on the returned values. Additionally it should mention all the return codes (could be partly Implicit Valid Behavior where the meaning of return code is uniform across all commands, at the risk of being more spammy for the sake of completeness). For more complicated behavior it might help in describing the behavior in more thoughtful and modular manner, and make it easier to review for completeness and accuracy, and it might help being referencable (analogously via VBID), which might also be useful for CTS organization and coverage tracking.