Yes, good isn't it?
The regulations state as you rightly note that "premium" cabins get the higher tax imposed. "Premium" being defined as a differentiated service over and above the basic product in service and fare terms.
And since they only have the "basic" product, they get the lower taxes imposed.
Example - BA, LHR-JFK, 9th Feb - Economy taxes £102, WTP taxes £142, Club taxes £142, First taxes £142.
MaxJet, same day, taxes £64.40.... of which the APD is £40. Ie, that nice Gordon's new lowest rate for a non-European destination.
From HMRC's website -
The reduced rates apply where the passengers are carried in the lowest class of travel on any flight.
Another genius move from the Idiot Brown!
TA