The stardate change was almost certainly deliberate. The new movie was designed to appeal to a larger audience than the Trek fan base. The story took place during multiple periods of time. Old-style stardate references, already meaningless, would have been too confusing to a non-Trekkie. Earth date-based stardates have some basis in reality, and they maintain the Trek "feel."
Changing the stardates makes absolutely no sense whatsoever. The new dates are EARTHdates, not STARdates, so why even pretend some futuristic calender system?
Stardates make absolutely no sense whatsoever. Whether they're the same nonsense as before or different nonsense doesn't matter unless you're a longtime fan who cares about this crap.
Regarding new audiences and non-Trekkies, do you really think they got the meaning of the new dates or that 2387 would have meant any more to them than 63395.7 would have? I'm sure to most of them they were just random numbers anyway.
To those who pay any kind of attention to the Earth years given in the movie and the stardates given in the movie, the new stardates would make some sense, and the old stardates would be a mess. To those who don't pay attention, they're just random numbers, so there's no harm in changing them.