I understand your problem but it isn't none:
PlanG import doesn't allow double entries which is a great advantage!
A message like "10 of 15 imported" means PlanG recognized 10 new userwaypoints and accepted them while the other 5 ones have already been imported with another csv file.
Basically I cannot exclude the possibility that some of my created userwaypoints have same names and coordinates and are placed in different csv files, they are just double listed. But this doesn't lead into problems. (no double entries possible)
This might have happened, but remember, the complete collection of my csv files holds about 5000 or more userwaypoints (POIs).