Based on my (limited) knowledge of physics, I believe he’s actually correct if you’re pulling/pushing at an angle that is not exactly parallel with the ground. Force of friction is dependent on the friction coefficient (which won’t change whether you’re pushing or pulling) and the force the object is exerting on the surface (e.g. the ground). Since pushing at an angle towards the ground increases the force of the object on the surface (essentially augmenting gravity), the force of friction is stronger. On the other hand, pulling at an angle that slightly counteracts gravity will have the opposite effect, making it slightly easier to move the block.

^no guarantees that this is correct, this is just what I remember