No HS or college or professional coach would agree with your interpretation of this. Mental errors are not knowing what to do. The facts of the game. The physical execution of a play is just that. Your technique a lot of times and your approach will determine the outcome of the play. This is true especially on routine plays. This is where you need to execute the technique you honed over thousands upon thousands of reps you have had to get you into this situation. Mental errors are typically those where you don't know what is going on. You execute the play however you make a bad decision. Such as trying to throw out a unforced runner at 3rd with two outs, while a throw to first ends the inning. A pitcher not covering first base on a ball hit to the right side. And yes, two outfielders colliding because one ignores priority.