My understanding is the same as yours. I suspect that oil was not given much attention in the context of autolyse since the classic French breads (baguettes, ficelles, etc.) don't use oil. In fact, according to Wikipedia, French food laws define bread as a product containing only the following four ingredients: water, flour, yeast, and salt. The addition of any other ingredient to the basic recipe requires the baker to use a different name for the final product. Oil serves to coat and lubricate the gluten strands and, hence, would interfere with the hydration process.