There's no such thing as 'DDA Compliant' - that's a very dated piece of legislation which is now only relevant in Northern Ireland (it was replaced by the Equality Act in 2010 within GB).
The trains would have been built in
accordance with PRM-TSI, however, the relevant part of the TSI (part
4.2.2.2.) isn't necessarily prescriptive about where the wheelchair accessible spaces have to be provided.
An alternative option would have been to provide the spaces in first class (with a free 'upgrade' for the passenger, such as in TPE Nova 3 and the 5/10 car Azuma), but, this can be problematic for passengers travelling in groups as some of the group would generally need to pay for the 'privilege' of using First class.