I think the main problem here is, that it is obviously not a publicly documenter “Ajax API” (yet), besides the blog post and some bits and pieces here and there it is not clearly documented. For our customer the reference/test implementation just stopped working last week, before that everything was fine. Now the returned response is not empty or anything, its just wrong, not up-to-date and reflecting the current inventory situation.
Now the customer cannot test this in detail and we have to postpone it.
The only other solution would be to implement it on the Warehouse and let it populate some metafields, which just does not make sense if we (theoretically) already have this information available.