Well it's your freedom to believe what you want, but here is some information from another site:
This specific GT3 thread from
GT3 Vault discusses the usability of the "X button approach". As you can see, it works for some and not others. With a 1 in 4 chance, it's mathematically POSSIBLE to allow a simple coincidence. I have never met a code that only works some of the time. The X button trick cannot possibly be a part-time code, and most of these people have probably been sitting there testing and reloading the save file on the last race of the series. But that's the word of half the world's gamers against the other. You decide.