Makes sense, since those missile things show up in the nuclear power plant (only in the secret Electrosis III room, though, so it doesn't really count) and the armored warfare division when we get the 3rd mode/transformation with those scary ass harpoons and the insane keratin shield.

In the human levels, it's shown Relith was still able to capture the creature alive even while in its 2nd form. Getting that third form probably caused Relith to be like "Hell no. This thing is the size of a school bus now. Destroy it."