Like most sites, there are public and "private" APIs. Publicly documented APIs are officially support. Private API can (and often do) change at any time, which is why we don't recommend they be consumed by customers.
Awesome to see this post, and your response here... I'm actually the author of the article.. Can you be more specific than "period"? It seems you guys have had coupon generation ability for quite some time.
They SHOULD have it released, no dispute about it, but it probably will take more than a few minutes, particularly for a platform their size. Between testing/validation and documentation it is not unreasonable to suspect that they simply haven't gotten to it.