I can see how someone could extrapolate Google's goal of indexing knowledge(JTB) into being a reliable source of truth. It's simply a matter of taking them at their word on the J and T parts. The B is up to the user.

Google's branding frames itself as the expert in the novice-expert problem. The vast number of users implicitly take on the role of the novice by virtue of using the product. They've already self-identified as a novice which makes both parties complicit in the arrangement.