Basically it comes down to quantization. Imagine an evenly bumpy plane, each bump essentially a classic particle. Its not like energy can't be split further, its just we measure a wave detector and look for bumps aka field excitations or a boson particle. All remainder becomes ejected short lived imaginary particles aka field excitations that aren't heavy enough to grip spacetime for long and maybe become tiny gravitational field waves or zip off so fast they physically phase out. If gravitons do actually exist, they may be instances of negatively displaced spacetime than what you define as energy. What's important is that we measure occurances of wave peaks of probability functions. What that means is that energy is not simply the ability to do an amount of work, but the occilating possibility to charge a field locally at recurring intervals of time. Also considered a String of information with a nonzero length. If charged too lightly, they dissolve as imaginary particles, on the other end, radio isotopes. Now you are going to ask for clarification for what is information. I assume it is nothing more than a localised type of antiparticle to however you quantize spacetime itself. Just as there was more matter than antimatter, there is seemingly infinite spacetime to the finite amount of energy. Annihilation yields nothing but the effect of frame drag as any information works like a black hole for spacetime but afaik gain no increases in magnitude. Kind of interesting, the antiparticle for physical information(anything) is literally the lack of anything given form, the vacuum itself.