The NHBC standards are not actually binding.
What the diagram is for is when different materials are in the same wall in this case a blockwork wall with bricks in it.
Engineering bricks are used as a dpc so this is acceptable.
Quite why though, they have a course of headers in the engineering brickwork I have no idea and some of the cut bricks at the corners are very poor quality brickwork.
Your snagging inspector does appear to have been very thorough!
And yes, you would have a long battle with DWH to get this rebuilt.
Please write to the CEO Dave Thomas and send him the photos and which region thinks this is acceptable. He will ask questions.
If you wait, you will have their excuses and reasons for doing nothing.
If the CEO is contacted it bounces back to the regions with a “sort this out” so you won’t be messed around by them.
david.thomas@barrattplc.co.uk