Wow, I wish I had a copy of the new and improved D1.1!
As a sustaining member, I might see mine in 6 months!
Just because the contractor is using a prequalified joint detail, it does not mean the WPS is prequalified. All the conditions of prequalification must be met and addressed by the WPS. If there is just one condition that isn't met, for instance the contractor elects to use something other than steel backing, all bets are off and it is a trip to the merry, merry pages of Clause 4.
Best regards - Al