The missing data/arcs deduced from earlier pings tells us either:
They don't have the data
or
They do have the data but don't wish to publicly release it [at this stage]
Knowing the round trip times for all pings, and assuming MH370 maintained a constant ground speed, plotting the course hour by hour would be a trivial matter.
It's understandable that INMARSAT doesn't publicly release all the data, but I suppose it's been made available to selected parties in order to guide the search efforts.