As parkfell says a JOC is not a regulated course. There is no syllabus, there are no prescribed hours.
The issue is that an MCC course can be run in a generic no motion simulator which may simulate either a jet or a turboprop and there is a perception amongst some employers, which I think is probably correct, that at its economical extreme, a cheap MCC course in a generic turboprop may give you the beginnings of a feeling for operating in a multi-crew environment but does very little to prepare you for the differences between operating light aircraft and jets in terms of capacity and handling techniques. This can be improved by using generic jet simulators or even 'real' simulators and including more handling time. Whether full motion is used or not seems to make very little difference. Whether this is treated as an expanded MCC course or as an MCC/JOC is just a marketing point. I would suspect that any airline specifying a JOC course prior to interview would also specify what they considered acceptable, either by recognising specific ATOs MCC/JOC courses as suitable or by setting out minimum standards.
FYI some ATO's advertise JOC courses which only involve 4 hours in the sim, two as PF and two as PM, some are 20 hours or so on top of the MCC (well done Oxford). There is a temptation to choose the cheapest, I would be inclined not to skimp at this point as the transition from single pilot piston to multi-pilot jet is the beginning of a new and very steep learning curve for most pilots.