I suppose you are right, although at “Buy 1 Roll get Three Free” then why not ???
In fairness, whilst I think it’s a little bit pointless, it’s not an expensive mistake..
The wider issue is this: nearly half of the houses here in Bristol are solid-wall. Insulating those with just 50mm foam-backed plasterboard would make an enormous improvement to thermal efficiency – say from 2.1 down to around 0.5. Yet this would not comply with building regs! External insulation is difficult when we’re talking rows of terraced houses in conservation areas.
I’d rather see lots of houses getting modest insulation measures than just a few houses get the full monty.