What is it about this investigation that is either "seriously embarrassing" or "deadly slow"? KNKT released a preliminary report 30 days after the accident (as per ICAO Annex 13 SARPs). The final report will likely take almost a full year to complete (possibly longer). Most of the "embarrassing" accident reports I've seen are because they were rushed or otherwise not thorough enough. Official aircraft accident reports are:
A. Extraordinarily complex investigations, and
B. Not intended to appease readers of pprune.