With the present post I will try to define more accurately the meaning of the expression in question.
slang. Inside information; the real facts:
learned the skinny on their falling-out.
skinny - slang term for inside or confidential information on a person or thing
skinny- information, usually accurate. When it is known to be accurate it is often called "Straight Skinny."
The skinny on
..." something is a relatively recent idiom that means to give the bare facts about something without a lot of unnecessary detail: a concise, detailed report on.