I'm not sure what your claim is based on. Epic members including Tim Sweeney and Cliff Bleszinski are among those credited for programming and designing them.
Also, if you're the copyright holder, no amount of contract work would take away from that, so you'd still have every right to not allow your IP to be used.
They may have done engine work. But the actual unreal tournament games were built by Digital Extremes. It is why they have periodically released the UT weapon skins in Warframe.
On the wiki page for Unreal Tournament they're listed as co-creators. In various live streams they've talked about how they created the weapons, maps, map modes and vehicle systems for the games.