This is like asking "What came first? The chicken or the egg?".
There is a lot of controversy upon this topic, yes, most scammers usually have low post counts because they are putting most of their efforts into talking to you and dragging you into their webs, but then there are the other 20% of scammers who go around posting a lot just to get a high post count, to seem trusted and then drag you down.
Then there are LEGIT people who go around posting a lot to get their post count up because if they dont, people usually wont trade them so they can get their first vouches.
As you can see, people NEED posts, as well as vouches to earn trust. Otherwise, how are leechers with no vouches going to get trusted? Most people do not trade leechers, therefore they get no vouches.
Im my opinion, post counts contribute a lot to trading in sythe, but are not to be 100% trusted, try to avoid larger trades with people who have high post counts, but no vouches. Im not saying to not trade with them, Im just making it clear to give them some trust, but not too much, at least until they get some vouches.
You may think I am a little biased, because of my post count and all, but I too am one of those guys trying to earn my first little bit of trust through post count, in order to get my vouches up and really contribute to sythe.