After reading the latest chapter we learn that the Five Tails is able to heat its or its jinchuriki's chakra to the boiling point allowing it to both strengthen its power and burn enemies. So does this count as the Boil Release? The boil release can effectively burn targets as it is an acidic gas the steam used by Han is a gas (basic chemistry :) So if it is true then Mei's version is just a variation of the nature like with the lava release or magnet release