An empathy gap is when someone can only relate to you when you relate to them, but otherwise does not respect the inherit merit of your points, thoughts or reason when you share a perspective from your own world.
It means they like what you say when your theory of mind reaches deep enough into their world to flatter them and make them feel seen, but when you speak from your own world and share its perspective, they cannot reach back to extend you the same level of perception to meet you as you meet them.
It is the spiritual equivalent of someone who likes it when a foreigner has traversed great distances to meet them, but who is themselves scarcely capable of leaving their own neighbourhood, and this asymmetry leads to a kind of selfishness where they cannot give to you like you give to them, as they fall in love with being seen by you even though they cannot even see you.
These people think they like you, because they like how you make them feel when you apply yourself to understand them, but they don't really like you, because they don't even appreciate you for you, only for what you are able to tell them about them. They appreciate your capacity to articulate the parts of themselves they are not even able to express, even though they cannot relate to you when you express you, let alone express you for you. You see, they cannot even accurately describe you to you - which is all the evidence you need to know how blind they are to you. You are not equals. They are lesser.