I have always gave the retention certificate to the dealer and had the car registered and delivered on my personal plate. This includes my current car and the other half’s which was just delivered in November from an Agnew group dealership on Boucher Crescent.
There is no reason why a dealer cannot do this. It’s the same as if they give you a choice from a selection of available plates when they are registering it.
Any dealer saying they can’t do this are either incompetent or just lazy.