As a Greek I can assure you that only G is an insult. Judging from this I would guess there are more mistakes there.
* The palm-outward vee has meant "peace" since at least the 1960's, and was associated with anti-Vietnam protests and the Hippie movement.
* The vee palm-in and tilted to the side also means "peace" or likely "peace out" or "see you later". Around since probably the mid-to-late 1990's and associated with hip-hop culture.
* The index and pinky outstretched is the "rock horns" (symbolizing demons or the devil), which you would use to mean "awesome" or "bad-ass". Around since the rise of heavy metal music (late 70's, early 80's).
* Winston Churchill probably used the palm inwards version until it was explained to him that it was a rude gesture.
* The 'archers' explanation is very likely wrong.
* You hardly ever see it in England nowadays, it's been replaced by the single middle finger.
As you say, it makes you wonder how reliable the rest of the article is.