What it means is that if you buy a boat/RV/Airplane, etc., it is delivered to you out of state, and you do not bring it into California for 90 days after date of sale, you don't have to show that you paid California Sales Tax (nor do you have to pay CA sales tax) to get it registered.
It was like this till 2004 when that period bumped up to 1 year. The new law drops it back down to 90 days.
However, you may have to pay sales tax in the state that you accept delivery.
Where you register it doesn't matter, and it won't affect CA Luxury Taxes.