The answer is about the traffic not the routes being processed. The routes processing is inbound for import and outbond for export, however the traffic on the node is been treated according to the imported routes, and vice versa. If You set up MED in export policy to have the traffic coming one way, not the other, then, the traffic is returned to Your network based on this(considering other node accept the MED from the node). It makes sense when You think of it, however the question is tricky.

Import policies affects the prefixes you receive. Prefixes determine the routes your network knows and would determine how you send traffic to reach them. Vice versa for export policies