Dictionary.com's Stone Cold and Stone-Cold Definitions

I'm really confused about something, and I was wondering if someone could help me figure it out. It's regarding the terminology of "stone cold" - having versus not having a hyphen between those two words. Why does dictionary.com, you think, have “stone cold” as being metaphorical (i.e., unfeeling, insensible), while “stone-cold” is defined in the literal definition of simply being very cold to the touch? Can’t they BOTH mean unfeeling, insensible, emotionless, etc.? Why would the hyphen change the possibility of being able to use it metaphorically? And, conversely, why can't "stone cold" have the literal definition that "stone-cold" has? Do you agree with dictionary.com in this matter?

Thanks.