I have a cunning theory to the Chassis No. Reg Date conundrum.

Firstly:
Some dealers didn't register the Aero's straight away. Possibly using them as showroom cars prior to the owner collecting them?

Secondly:
Owners are assigned Chassis Numbers based on build slot. Due to Dealership priorities and some Owners keen-ness, particular cars were moved forward in the build queue... getting built out of sequence therefore registered early whilst bumping/gazumping the others (or particular ones) backwards?