OK To Use This Male/Female Jack Combo For 24 Volt DC?
Only the manufacturer knows why these connectors are rated for 12V usage. If you use them at 24V you are on your own. The connectors might fail immediately or might never give you any trouble. If they fail they could fail into a safe mode, simply cutting off the flow of current, or they could catch fire.

We can give you an opinion about using the connectors outside of their specified operating range, but we really don't like to rely on opinions and assumptions as engineers.