Why shouldn't they be sending at least monthly reports on their progress to their superiors?
1) They don't HAVE any superiors. Genesis was a civilian project under Carol Marcus' personal control that needed the Federation only for funding and research grants (which they got in the form of Reliant and assistance from the Starfleet Corps of Engineers). It was nobody's business but Carol's HOW Genesis worked, only THAT it worked, and to what extent.
2) Stage One was evidently completed without any Federation assistance at all, and the Genesis team was just finishing with Stage Two when Khan showed up and killed everyone. The actual Genesis Device -- which was to be used in Stage Three -- was just a prototype that had never actually been tested before: much larger and much
more sophisticated than whatever device they used in Stage Two. It's not even clear at this point that the Genesis team had even furnished their final reports on Stage Two (hence the lack of updates in the Enterprise computer) which means they were still monitoring the Genesis cave, collecting data on the progression while they were waiting for Reliant to find a test site for Stage Three. If the novelization of TWOK is any indication, that final report would have been EXTREMELY pessimistic once it was realized that the genesis matrix was so inherently stable.
IOW, they did NOT provide component-by-component reports on Genesis to the Federation because that data didn't belong to the Federation and they had no right to receive it in the first place. Compare with the COTS and CCICap programs NASA uses; the SapceX company has to demonstrate certain milestones if they want to receive continued funding, but they sure as hell don't have to furnish NASA with detailed blueprints and design notes on how to actually build and manufacture a Dragon capsule. Not purely because that information would be useless in the absence of a specialist who knew how to interpret the data, but because that information is proprietary and NASA has no business asking for it unless they have a legitimate reason.