There are some good reasons for believing such a hypothesis. First, it seems implausible that the first humans would have innately known a language. Of course, it is not beyond the power of God to have pre-programmed the first couple. However, since no human being that we know of now is born with language innately known, it is more likely that the first couple learned language and how to use it just like everyone else. That is not to say that Adam and Eve could not have had minds with an underlying grammatical structure that was known at consciousness, only that they would have had no language with which to fit that structure.
Consider how we know purpose. One cannot know purpose without knowing language since purpose requires thought and thought requires language. This is because thought is intentional. A paperclip is, in itself, not an intentional thing. A thought about a paperclip, on the other hand, is intentional.
It is possible that God pre-programed Adam and Eve to recognise the purpose for creation and specific parts of it. But to do that they also would have needed to have language pre-programed. There are a couple of problems with this.
First, if God had pre-programmed language and a correct teleology into the first humans, why not program it all in? The first chapters of Genesis tell us that God did quite a lot of explaining about what things in the garden were for (trees and fruit were highlights of this discourse). Indeed, the first humans evidently had to have their own purpose explained to them (Gen 1:28-29). But if God had pre-programmed them with language and the ability to recognise and know the purpose of everything else, then why tell them these purposes explicitly? Far more likely that they did not know and had to be told.
Second, a preprogrammed language may not be possible. A language is only known between people. It may be possible to postulate a pre-existing soul that communed with God, but this is implausible at best. Added to which only Adam and possibly Eve would have been taught language in their pre-embodied state. Everyone else since then has learned language after they were born.
If, then, Adam and Eve were taught their first language by God and God taught them about creation, its purpose and their role within it, then we might be able to say something about how we know these things. We can at least say that human language originated in God's speaking to human beings. God taught Adam and Eve language. It is likely that the first couple passed on information about the world to their children. As they taught their children language they taught them about purpose, about God, about themselves. More than likely their explanations sounded a lot like God's. This leads to an odd thought - when you and I teach our children about the world to some degree we are passing on an explanation that God gave the first human beings.
More importantly we can say that it was necessary for human beings to be told certain things about creation. We did not work these things out for ourselves. For example, human beings need to be told, by God, what things are for. Just as Adam and Eve could only know the right interpretation of creation because God told them we too need God to speak to us. And if that's true then the Bible (being the word of God) is, in the same way, the explanation of creation that human beings still need today.