Twins are way too much for such a short rake. Single WDP4 itself is capable of running this short rake at MPS on this section ( Since it is a newly opened section, MPS will usually be low until tracks settle in after some use) or any section for that matter.
Most likely, since this is the first passenger service, and there will be no good loco availability on this section in case of Loco failure, Twins might might have been provided so that one loco can takeover the train if the other fails.