Incidence matters. If intentional classified information leaks were commonplace and unsurprising, then sure, we could say we expect retired military officers to routinely follow the example of Trump, Snowden, and Assange when it comes to classified information. But I don't think any of us can make that claim.

Intentional classified information leakage is relatively uncommon, and, for the most part, is punished when it happens and a perpetrator can be identified and caught. Obviously in the case of Trump, that potential punishment is politically fraught, as was/is the case with Assange. The US government would love to punish Snowden if they could get their grubby hands on him. I guess look to Chelsea Manning if you want an example of when the government has successfully brought down the hammer on someone doing things with classified material that they didn't like.

To bring it back to the topic at hand, I expect that the retired military officers now taking employment with the Saudi Arabian military will most likely protect any secrets they're legally bound to protect. Why? Because that's what seems to happen most of the time, and punishments for failure to do so can get pretty severe. And someone who wanted to sell secrets might have a difficult time if their chosen country of exile is SA. If found out, they'd have to contend with the strong possibility that the SA government would extradite them to the US, depending on what kind of pressure the US might bring to bear.