From my point of view, plugins developed as "feature as plugin" that are not included in the current version of the core and are planned to be added to the core at some point in the future, are out of the scope. These plugins may or may not be finally added to core and can change a lot from now to then.
I'm interested on what the community think about this because of the comments on this question.
First off, we (as in "the community") currently have the stance that those plugins are in scope as much as discussing core patches and Trac ticket code is in scope. The reason is simple: StackExchange is a wonderful system that allows to off load problems and present them to a wide community to find a variety of answers that might bring points of view that else wouldn't come up - and let the community vote on them. Bringing development question here is our main goal and discussing future core (or current feature plugin) development is highly appreciated.
In short: Please don't nuke such questions.
I think the criteria if a plugin/theme question is off-topic should be if it can reasonably be answered by the people actually participating in answering questions here. Featured plugins are almost by definition are both beta quality software which is in a flux of change, something that prevents people from actually being experts in them and they have very little users.
It will actually be more useful to answer yoast SEO, jetpack, w3tc and woocommerce questions, and there are probably more people that have expertise in them around here, then answering featured plugins questions, but I see the value of having a simple line drawn between what is on-topic and off-topic and I don't see the value of blurring this line for the featured plugins.
FWIW the json API in its current state is just a piece of bloat. It took me less time to implement a subset of the functionality that I need then the time I was willing to allocate to wade in that bloated code.
If that question would have been worded as "how do I create json API to retrieve a CPT" I could have answered it with a "built your own" solution, and someone else could have answered it with the json API plugin but as it is a bug report for the plugin it should be better handled in the plugin support channels in the same way I direct people to trac when they ask about bugs in wordpress.
