@Muran
IMO this road is just a Trojan horse to enable the planned commercial exploitation
Or, an alternative theory is that the airport want to get the road in quickly before it gets covered in houses (and therefore any substantial road becomes impossible)
It will split* airport traffic... ...early reducing the need for a long dual carriageway section.
My reading of this is that they want a dual-carriageway through the housing before it's too late.
*The word "split" here is misleading, implying that traffic will be divided between the two roads, when in reality the traffic will in fact double, per the additional capacity created.
@jonty
The second runway is being used for car parking (and plane parking). See the second picture here:
https://www.edinburgh-airport-eastern-access-road.co.uk/the-proposals
How ironic.