This has nothing to do with tubeless vs tubed and, contrary to what the other posters are suggesting, regular tubes and tires CAN be run in UST rims. I guess that's why you never trust a Performance sales associate...
In any case, as for your question... You're fine on any new rims you can buy at a bike shop. "hooked" rims refers to older rims, some of which were straight-sided (vs. hook-sided) and would therefore not hold a tire as securely as a hook-edge rim. You would actually have a pretty tough time tracking down a straight-sided rim today, they're pretty much a dead standard.