I have found a page in which a sravaka seems to object to a mahayanist that, if those that aren't ordinary people have no cognition, then it's ultimately correct to have sexual relations with a forbidden woman
If he says: Madhyamikas make statements such as the following: "[Cognition] is not in the eye, it is not in form, and it is not between them or in both of them. Wherever it might be present, it neither exists nor does not exist". So no cognition is apprehended.
The footnote says that the source of the quote is unclear, and not from MMK or Aryadeva. Bhavaviveka then seems to explain that the sravaka's conclusion, that forbidden women would then be ultimately correct to have sex with, is not proven, because it is no different to saying that all women can relieve desire: both are examples of improperly denying all things.
Bhavaviveka and his Buddhist Opponents p129
So, I think the general argument is that ultimate reality does not deny conventional reality. Even if distinctions do not ultimately exist, but do conventionally, that does not mean ultimate reality denies the truth of conventional distinctions. The difference is about being and not truth.
It may be worth noting that "non conceptual cognition" crops up a lot in the book, I think as the goal of Buddhist practice.
I'm not sure if I've misinterpreted the argument: did any Indian Mahayana Buddhists, such as Bhavaviveka, have non-cognition as a goal? And, would that mean they do not seek knowledge, or just that cognition is empty of svabhava?