My best guess is that his link to Jodie becomes more noticeable when they actively collaborate. It's not hugely uncommon for lost souls to wander near a rift (as seen in Black Sun and the Alone ending) so it might reasonably be assumed that the entities assume Jodie is speaking to herself (hardly rare for a person to converse with themselves in private) or nearby humans until and unless Aiden then acts on her instructions or he directly interacts with her. If Aiden 'appears' to be another lost soul there's no reason he or Jodie would be especially interesting without interacting.
Even assuming that Jodie is individually and independently gifted (supported by both of her parents having gifts but nothing akin to Aiden as well as the Alone ending) such individuals are unlikely to be exceptionally rare. Remember, the DPA existed well before Jodie, well after, and was very well funded none of which is likely without some concrete confirmaiton and use for gifted persons (implying their gifts are not hugely rare and can be measured and studied with some accuracy).
So, basically, being psychic isn't that unsual and Aiden and Jodie blend in when they don't interact with each other or otherwise cause a fuss.
