If an .EXE is modified and is used to race against other people who have unmodified .exe 's Then Ok maybe "cheating" is too strong a word for it, But the fact that it would be "possible" to do is wrong.
So ok, Perhaps not cheating in that sense.
The idea of modified .exe's that have been approved is that those .exe's should only work on servers running the same modifications, Obviously that has not been the case (even though that was the intention) and this seems to have been rectified today.