Any flight time gained in SEP aeroplanes and recorded in a logbook as P2 will be ignored for licensing purposes by the competent authority.
B4 digging into the details I would have second that, but now I am not sure this holds under all circumstances (unless you encounter a bonehard ignorant authorities clerk).
If you have a single pilot
certified SEP, whose actual
operations requires a second pilot - as there are some occasions we already identified by the IFR requirements for aircraft without 2-axis autopilot in certain countries - how to deal with that? Open question, as I am really not sure.