This is how I understand it now...
Let's reduce the sentence to the simple present.
This is the same as:
Notice the infinitive after "has": "to be". It is sometimes possible to use a construction called the "perfect infinitive".
This sentence sounds OK to me, but it sounds unnecessary to use this construction. It seems to me that you can just use the infinitive rather than the perfect infinitive.
So the question is: why must you use the perfect infinitive? I'm finding it difficult to find any explanation online of when you use this exactly. I've found this. It can be used when referring to things in the past or future.
However, the important point in this particular sentence is that "have to have known" is the same as "must have known". These are both used in the sense of "probably know". "He has to have known" = He probably knew.
OK, now turning to the "had".
Adding "would have" to a verb changes it so that it refers to something hypothetical in the past, i.e. something that didn't happen in the past. Example: "I would have gone to Spain with them but I caught a cold."
So saying "the benefit would have had" instead of "the benefit had" means there was no past obligation regarding the benefit. It's discussing something hypothetical in the past.
So I think this sentence is possible:
It's referring to a hypothetical past probability.