On the other hand... be liberal in what you accept. JSON::MultiValueOrdered was written with that principle in mind: to accept JSON documents that contain multiple values for keys or rely on key order. But it also allows them to be round-tripped.
Either way, it's a SHOULD and not a MUST. (Except in the I-JSON spec, which I think you missed out in your comparison of specs?) As long as you know what you're doing and have valid reasons to do so, you can forget SHOULDs. And if you're using JSON::MultiValueOrdered instead of JSON::PP or JSON::MaybeXS, it's probably for a reason.
Also, bear in mind that I started work on JSON::MultiValueOrdered more than seven years, so it predates all the JSON RFCs (except RFC 4627) and ECMA 404. The format description on json.org was also a lot more concise back then.
