Useing 20A receptical in place of a 15a
Min, it really is just semantics, but the possibility is there.
The problem is you have the potential to plug in a single item that is over 15 amps. Such as a power tool or large room A/C.
Why I say it is semantics is because what is the difference between that and plugging in two smaller loads that equal over 15 amps? Not much, but the chance that a single item with a 20 amp plug will trip a 15 amp breaker on a regular basis is pretty good.
The opposite is the basis of the code about using multiple 15 amp receptacles on a 20 amp circuit.
First of all there is almost nothing in a home that will have a 20 amp plug configuration, 'cept maybe that A/C or power tool.
The though is that if an appliance has a 15 amp plug it will not draw over 15 amps, but more than one item will. So code lets us us multiple 15 amp receptacles on 20 amp circuits. One of the 15 amp receptacles will not overload since the plug is only 15 amp.
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.