As long as it can finish before it gets too cold where you are it was just able to get a bit bigger in veg before the flower shift. Same as if he just flipped to 12/12 for two weeks earlier than you for indoor photo grows.
His thinks its later in the season than it actually is. This could be an advantage in colder climates if you have problems getting em to finish outdoors before the season ends like longer flowering sativas. Or get to smokeable bud faster. Cant see it hurting anything, end of season temps permitting and its all light and not nitrogen related.