They were mentioned in Piye's triumphal stele at the siege of Hermopolis, but the translation is tentative, I have no idea what they looked like and the text dates to the 25th Dynasty, predating our timeframe by more than 200 years, so I'm not really arguing to add catapults for the Kushites or anything. Just an interesting mention of stone throwers at a really early date, a generation after King Uzziah's stone throwing devices just a stone's throw away in Judah.
I strongly agree with Rams for every civ though. They're not exactly marvels of engineering so they can be the generic go-to siege engine for everyone. More specialized sieging civs like the Greco-Romans have enough unique siege options to continue standing out enough as the best in siege. It's just that advancing with elephants alone is really difficult if you're up against players that know what they're doing (slinger can even take down a fortress, imagine what they can do to an elephant...).