In our Presbyterian church (and most every other church you mentioned) only active members are included. The people in the pews on Sunday are who are being counted as members.
In fact, when you move you transfer your membership from the previous Presbyterian church to the new one. There's no place for padding the numbers.
It's not about numbers. 8~)
I certainly don’t KNOW.
I have heard about RC churches doing it and I’ve heard about some Baptist churches round these parts doing it.