Author is a bit wrong about the heating. It doesn't maintain a constant body temperature, it maintains a constant body temperature relative to the water temperature. It'd be like if it got 10 degrees colder outside, human bodies stayed at 88.6 instead of 98.6
For the extra page on this one, you should be careful about using the terms "tentacles" and "arms" as they aren't interchangeable in biology. Squid have 8 arms and 2 tentacles, octopi have 8 arms and 0 tentacles, and vampire squid have 8 arms, 0 tentacles, and 2 "filaments" that function...