A more concrete example may be useful to explain what I’m thinking. A company has you click to agree to their TOS. They link a doc, which is of course quite long. That doc has a footnote which links to another doc. You do not read the secondary doc, and it is the contents of that doc that allows the company to sell you data/prevent you from suing them/harvest your organs/abduct your family/whatever. My point is that “I did not read the document” should be a valid defense, such that if it is not I believe the law around this is wrong.
I suppose you can claim I am wrong to believe that, but it is accurate for me to state that I _do_ believe it, which is why I didn’t list me being wrong as one of the possibilities. Practically speaking, that is the first possibility I enumerated.
I should note that in my example, imagine neither doc is any more inscrutable than all the TOS we encounter in the wild, instead it is the construction (the fact it is a footnote link) that makes it easy to miss the additional doc.
Incorporations by reference are not unusual in contracts. A contract is unlikely to be voided merely because the contract has references and the counterparty didn't read them.