I don't think it's as important to worry about the older party involved and whether or not it's paedophilia but whether or not the younger can be of sound mind or make an informed decision legally to have sex, which is obviously why statutory rape or that specific sexual assault exists.
The only real factor involved is whether or not it's exploitation or not - the age is just a legal frame that's used to make things easier. That said, most things related to sex is often heavily linked with exploitation at any age, at least in debate (prostitution, pornography, etc.).
I think most people would agree, though, that it's pretty silly that if (using our age of consent) one person is over 16 and the other is 15 but a few hours away from their 16th birthday that those few hours constitute the difference between statutory rape and paedophilia and perfectly normal sex. Then again, you could use that argument about something like being slightly under the drink-drive limit and just over, so meh.