Doesn't a normal distribution typically arise during random sampling? I.e., if there's some statistic you calculate based on a sample, then when you take a bunch of independent population samples, that statistic will tend to be normally distributed over those samples.
If that's the only reason we'd typically expect to see a normal distribution, then I don't understand why we'd expect employee ratings to be normally distributed.
But of course it isn't randomly distributed because you hope you recruitment process isn't just picking up random people from the street.
So yeah, it makes no sense - it's just cargo cult business school science.
But you can make a plausible argument against the performance metric being normally distributed among your employees because that would mean the way you hired your employees was completely random with respect to that performance metric.
I don't think there's any reason to believe that employee scores (out of 100, say) should be normally distributed.