Boeing probably doesn't like having folks looking over their shoulder and demanding specifics.
The ham handed way they rolled this out and responded has resulted in a lack of trust by their customers. Apparently it hasn't occurred to Boeing that they have to work to regain that trust.
Obfuscation is the by word. I suspect that the Boeing strategy, for a long time now, is to avoid any scrutiny they can that could further delay RTS. The 'bitflip' problem was a fly in the ointment that has made it more difficult by delaying RTS for while.
Just about anything suspect identified by any of the reviews, or by congress for that matter, whilst the grounding continues, would make it more difficult to achieve RTS, whereas, a finding after RTS is actually unlikely to result in the grounding being re-instated.
I suspect we can see this strategy of obfuscation in providing data to congress (ostensibly due to IPR) and congress themselves agreeing to forestall Boeing attestation until post RTS. We have also seen it in the apparent delay in providing data to the Indonesian Authorities for completion of their final report. We have seen it before in relation to the JATR, where the excuse was initially IPR issues that has delayed submission (it seems until August having been established in April), and now we see the submission was not as required by the panel - further obfuscation.
So, it would seem that in all cases, no further findings will be available until October and probably post RTS.
It should be remembered that all these bodies are legally constituted and submission requirements are legally sound. That included the JATR that is constituted by the FAA to perform a review scoped by the FAA who are Boeings regulator and they are obliged to provide data so required.
I think you are missing a key point - and this is unlikely to be obfuscation:
1st, while I understand that three different advisory or investigation committees have been set up; their legal basis and what they can request does not give them absolute authority to request everything.
As an example: No aircraft manufacturer is required to submit detailed blueprints or the exact software code to the FAA for certification. They are required to submit the function of different things and evidence that their design or software meets that function.
On the other hand; the NTSB (and equivalents in other countries) can request and get those detailed design documents, calculations, software code, etc. for specific items that are believed related to a crash or significant failure in order to provide independent analysis of adequacy and if they contributed to the crash or significant event. They cannot request that kind of information for other areas or features of an aircraft (vehicle, bridge, etc).
So, Boeing is not required to supply everything to these boards; and one of the things likely discussed and agreed upon up front is in fact just what kind of information needs to be supplied for the advisory or investigation board to do its work. If you look at the assigned task of each of those boards you should be able to innately see that they require different kinds of information in order to carry out their different tasks.
A second key factor is that such investigation boards often request more information later based on the initial submitted of information from the 1st request. I've been involved in some nuclear industry reviews and there were almost always 3 rounds of request and analysis of information, and sometimes 4. Root cause investigations typically have between 3 and 6 rounds of such request for the areas of interest (1st and 2nd submitted information are used primarily to rule out possibilities and things - so that you can do detailed focus on the areas where things did not go well during the event; and then you keep mining until you fully understand the impact of that area of "non-ideal" performance, and the significance of it to the event. For the root cause item, there is often sufficient information and analysis to explain exactly what and where the failure in that issue/item was.
Thus, it is not a surprise at all that the Indonesian Investigation Board has requested additional information from Boeing on something. In some cases such information is not readily available (just send them the file) and perhaps specific testing or obtaining information from other parties is involved.
Third: Certain countries like to get as much detailed technical information (design documents and software code) as possible. I have done work in China and I assure you that a key goal is to collect "know how" and "how is it done" for everything they can from other countries. They are not unique in this - just the most aggressive country I know of. So, I can easily see China requesting information that Boeing will never supply as its proprietary intellectual property that is not needed for the tasks of the advisory or investigation board.
Have a great day,