2D
The holder of an ICAO PPL is deemed to meet the aeronautical experience requirements (with certain caveats) for the issue of a self-containd FAA Pilot Certificate under Part 61.75.
I am reading 61.75 and it describes a piggyback license. This is probably just terminology but I wouldn't call it "self contained"; a standalone FAA PPL needs additional training over the UK PPL training, plus additional night requirements, plus a written, plus an oral plus a checkride.
Obviously you know this; I am writing this for the original poster.