Hi MarshallArts
I cannot directly answer this as I don't use the SDK to access their endpoints - for the reason that you are at their mercy to how the code works for accessing endpoints.
I have a client using jobs, sub jobs etc - and I can have a look at a page extracted from the endpoint as post it to you - it should then give you perhaps a bit more info about your query.
The other thing you can do - simply code up a simple form in VB.NET with the jobsregister endpoint to see the json payload you get back - it should help you further.
Re my client - I may not extract the data to the depth you do from the jobs register but my client hasn't had any problem - and jobs are extremely important in my package.
The Doc