Obviously companies think it is worth a lot for certain employees to be quiet, so they pay accordingly. There is no "should" going on here, there is only what the two parties agree to.
They should pay him whatever he would make going somewhere else. Expecting someone to not work in their career field for 1-5 years and not get compensated for that is silly.
LOL - you have stumbled upon the pay grades for security and executive management directly ! they absolutely are paid more to participate but stay quiet. It is a daily requirement.