Earlier quoted context omitted.
They ask these questions to me all the time and I'm a (non-dual) citizen. The EU and especially the UK is more intrusive about their questions. Switzerland is/was the least intrusive. China never asks me any questions, but Thailand and Japan might.
My experience in the EU is that, even for EU citizens, the UK and (a somewhat distance second) Spain can be quite intrusive. For the rest of the EU and Switzerland, they almost never ask anything. But I definitely agree that China seems to be the "easiest" in this sense. No questions at all. :)
Entering France: takes my passport, opens it, stamps it, no questions asked
Entering UK: tons of grilling, return ticket, etc, etc
That's with a non EU passport.