Failure to write up a report concerning firing their weapons is, perhaps, in your view... an act of ommission and not necessarily... "falsifying"?
They weren't convicted of falsifying or failure to report. They were convicted of obstruction of justice.
In this case it sounds like the supervisor actually appeared in court AGAINST his subordinates ~ which is sure a strange place for a supervisor to go to correct any problems he should have corrected earlier.
If every government employee (cop, auditor, regulator, etc.) were expected to be perfect first time out on every report up the chain of command, and when they weren't that we simply prosecuted them for felonies, we wouldn't have any government employees ~ NOR CONTRACTORS GREED BALLS ~