I dont think that he's going to do that. He made such a mess of defending himself on TV, Im sure that the Royal advisers are nervous of what stupid things he might say to the FBI...even if he's not guity of anything...
besides, its pretty obvious that Andrew doesn't notice things that much He may well feel that he doesn't remember anything that might be helpful so its best not ot put himself into talking with a bunch of FBI agents. HIs arrogant attitude that he just expects there to be "people around him" and his rich friends, who are - servants, masseurs, asistants, dogsbodies … and he does not really see such people.. so he is not likely to come out with anything helpful.