The WP Documentation is known to many developers, and Steem´s API should not be a problem for any low-mid skilled developer to understand if it is documented correctly.
Once a developer see this post and understand how much money he can make - trust me, he´ll start making it ;)
Money is Power.
You hit the point pretty much, there is no documentation of the API. It is only known to guys coming from BTS or insiders, but yes in itself the API is not that hard.