The turntable is there because the microwaves bouncing around inside the unit don’t do so completely evenly; there will be spots that don’t get heated as much. Moving the food around inside the unit makes it so one of those cold spots isn’t consistently in one place in the food.

So with that as a context, if a cold spot is at or near the center of the turntable, it’s not going to get moved around in the food when it rotates. So better to put the food away from the center.

Fun experiment: take your turntable out, place in a large plate with pieces of the shittiest American cheese slices. We are talking kraft single serves. Splay them out, no deeper than one layer thick is needed, but make a full cover of the microwave bed (on top of the plate though. You will make a mess if not). Then you simply cook the shit out of it. You will see the cheese bubble and burn in the microwave wave peaks and you will see cold cheese in the wave troughs.