T-Rex has the algo optimised maximum that is why no private miners or no new faster miners for X25X.
t-rex is not optimized to the maximum.
why not make a faster one to prove?
If I release a faster kernel the closed source miners will use a couple of days, steal my hard work and put a 1% fee on top of it.. Bad for business. But on the other hand, if nothing is done about the speed, gpu mining for small gpu miners in many of the well known algos could be history.