Huh, ok. So the purpose of Bubbles is to convert them. The way I was looking at it, their purpose was to sometimes randomly move stuff to get additional matches, and you can hopefully remove the correct Bubbles also completely by random using Ice or Elec. Which would make them extremely high variance. But it seems the intent was "these are extra Freeze or Shock gems in the future, but in return, there's a bit of initial randomness."