I'll assume the EP DHs who FOSed O-5 were EPs on a competitive FITREP, otherwise some people have a gross misunderstanding of boards/FITREPs.
For a more fine understanding, an individual trait average below the RS cumulative can completely negate a competitive #1 EP. Yes, some RSes have done this, and it sends a very specific message to boards (or boards interpret it a certain way).
I don't know why particular EP DHs FOSed O-5; I'm just offering a possible scenario in the "there's more to the story" category.
I don't expect those who FOS'd to dissect their career fitreps in a public discussion to give validation to the results of the board...It doesn't really matter what the more to the story is, it matters about the optics.
The big message that JOs are receiving is there's no really value for them to stay in a being a DH. 10 years ago it wouldn't have contributed to an attrition problem for the Navy, the job market sucked and folks were motivated to stay in for 20 for the job security and the pension. Today, it definitely will- especially on the pilot side of the house.
I'm not sure folks who are still deep into the system understand how easy it is for pilots to get a flying job on the outside these days. Majors take some prep work but literally, if a military pilot (jet, maritime, Helo, whatever) decided to test the waters and publish an application to the regionals at 2330 one evening- they'll have interview invites from most within 24hours, outliers are a week. Other parts of the industry are showing a quick turn around as well.
I posted one application at around 130am and got woken up to a call to conduct a phone interview the following morning...
If the Navy makes it appear overly difficult for folks who are burning themselves out staying on path to succeed, and makes the metric it takes to reach success undefinable, folks will just get out and go somewhere where career progression is easily to understand and they're compensated for their efforts tangibly and stay reserves for the medical and comradery and beer money as well as the pension when they're older.
No bonus amount will matter to most folks if they can't see themselves progressing in their careers and job opportunities are plentiful on the outside.