This is a really strange thing, because to me a Swede, that means that whatever has been signed is not a contract at all and is, well, who knows what.
To me a contract is an agreement. If it is not specific, then it is not a contract at all, and if it's changeable, then it's very obviously not a contract at all.
I've heard of more of this kind stuff with US healthcare, although I'm not sure I even want to understand the ideas there, but when people start messing up the basics of laws, refusing to rule that things which are obviously not contracts at all are not, or accepting other weirdness, then they start destroying the law itself, because people will try to build on these things and it'll become a completely arbitrary mess, where almost anything is suddenly allowed. I don't understand how US lawyers etc. could make this. One would imagine they'd want contract law to be a thing, but apparently not.