There’s normally some slight wood movement caused by temp and humidity changes during shipping, especially airfreight, so it’s best not to do any changes or sanding to the neck area until you’ve had the kit acclimatising at home for a couple of weeks. After that is the time to decide whether you may benefit from some light sanding. But a neck doesn’t need a great amount of finish on it, especially on the sides of the heel area where it’s going to be well protected so you can always simply apply less finish in that area. As Fender3x says, snug is good, so you need to be careful with any sanding that ‘snug’ doesn’t turn into ‘loose’.