User blog comment:PerhapsTheOtherOne/Speculative Spitballing: Goliath/@comment-4010415-20150608182803/@comment-25555436-20150608200203

In Japan, "Kaiju" has it's own classification. It may be broader, but not all monsters are considered Kaijus just for being monsters. There are other specifics they need to reach to be considered a true Kaiju.