They're separate entries in the "our technology" dropdown on their website, and the "Natrium" section specifically calls out that it's the fastest-to-market option, with a design that sounds essentially done, while the TWR is described only having a "core concept design" (which sounds like marketing fluff for "not close to being practical yet" to me). The renderings of the inner workings also look totally different from one another.

On their website I only see the claim about using depleted uranium for fuel on the TWR page. Where do you see those claims being made about this reactor?