Yes, they don't care, you can use any QR you want. I've used an early SON28 with the stock one, a Pitlock, an external cam light skewer, and various Shimano skewers, and a current SONdelux with the stock one and a Shimano QR. It doesn't matter.
I don't know the numbers but I believe internal cam skewers develop quite a bit more clamping force than bolt-down skewers, so in other words it's conceivable to make a hub that could care about this distinction. But Schmidt hubs don't.