I think people really, really don't know what a lock is in MMA. But as a pointer, whenever there are changing circumstances between a fighters previous fight and this one, it's never a lock in their favour. A fighter recovering from injury, moving weightclasses, having a long layoff is never guaranteed to perform the way you expect them to.
Additionally, we have no useful data of common opponents between TJ and Cejudo so we really have no idea just how they match up. TJ is likely the favourite, being a bigger guy with great TDD, but that doesn't guarantee that he can't be taken down and controlled with a harsh weight cut hampering him.