Earvana nut, buzz feiten etc are methods of scale length compensation. Guitar tuning is based on equal temperament so it will be out of tune by equal amounts in all keys. What earvana and buzz feiten try to achieve is, make the guitar sound more in tune in the guitar friendly keys like E, A, D, C etc, the sharp keys basically. To put it in a negative way , it is like 'rearranging' the problem on the guitar.
Scale length compensation is also used by PRS, melancon and some other hi end makers, no big deal actually considering how many people mess up their intonation using harmonics on the 5-7 fret.