Hi,
That thought is technically not really wrong.
By creating the normal maps functionally inside UE, you save the memory for and streaming overhead of the normal map texture.
It is just that the gain of this is less than the performance loss due to more extensive calculations on the material.
I doodled a bit around with the material editor and created a checkered material without the use of any texture. 
But I doubt that it will be in any way more efficient or performant than using a small texture.
(In this case, actually a 2x2 texture would suffice).
Cheers,
Klaus