Actually Shakespeare had the best answer for this: "A rose by any other name would smell as sweet". Just because you know HOW matter is constructed doesn't make it any less real so the physical world exists very much, calling a solid object energy won't stop it from being a metal and feeling solid or interacting with other objects with all the properties we expect from a solid object. While the concept helps in better understanding of molecular physics, you can't apply it to regular physics and it could be misunderstood if you apply it to philosophical concepts which I very much doubt Einstein was doing there.
