On a side note, curing grey EXOT with ELEC is like trying to cure cancer with radiation: enough to kill the cancer, but not enough to kill the patient!
EXOT + AMTR = PHOT is normal, AMTR + anything = PHOT. As for EXOT + LOXY = OXYG, this is probably just the EXOT turning into the LOXY it touches, and evaporating it with its heat. An observation I made: The contrast of white/black bands mirrors heat gradient display. EXOT's color measures heat, but grey EXOT apparently measures heat FLOW.
This has been known for a long time, but well done if you discovered it for yourself. It's something that could potentially be really useful, but people don't make good use of it because it takes quite a bit of ingenuity to make it behave exactly as you want to. It definitely has applications to devices that either construct or repair things, but either CLNE, CRAY or DRAY are simpler and easier to work with.