Its almost impossible to answer your questions without having this bike!
For the rear folding rack, the two required mounting points are present (hole on the main frame in front of the seatpost, mounting tube on the rear suspension arm).
Now, there is a major difference in building a Brompton frame clone and a Birdy 2 or 3 clone: the Birdy 2 and 3 (with exception for the Birdy World) frame are not made of tubes, they have an hydro-formed frame which requires a special tooling to be build. This tooling is quite expensive, its cost must be amortized in the price of the bike and a relatively big amount of bikes is required to amortize it without increasing too much the bike price.
I wonder how they solved this problem, could it be that they could reuse the Pacific Cycles tooling of the old Birdy 2?