(1) Rayleigh: certainly not. Who said independent distributions horizontally and vertically? Bad idea. Easy to see your arm, body and the entire throwing movement is not split into two independent dimensions. All the little bits, joints, muscles and sinews conspire to mix up the two. (Carefully follow the path of a laser pointer in a trembling hand, for example.)
And what do you get if you mix up a lot of causes? The Gaussian, indeed mr. Kolmogorov.
(1b) Hitting the aim point zero probability: yes, duh, that holds for any point in any continuous distribution --- yet some point is hit in the end, yes? If all points have zero probability, nothing must be hit. Hm... flaw.
It's that pesky infinity thing. Ah, maybe we're not dealing with single dimensionless points in space?
(2) Any darts player knows the spread is easier to control horizontally than vertically, so squishing the bivariate `elliptic' curve into a univariate `round' Gaussian is a sin. The article sounds as if they've done just that, `measure distance' and not the vector of horizontal and vertical distance, but that's not proof this is what they did.
That said, the `Letters' submitters should have been pointed out their obvious mistakes --- one mixes `gaussian' with `uniform' distribution and misses the whole plot, the next could have been hinted that 2D gaussians give exactly the ellipses of equiprobability that he experiences.
Certainly since the `Letters' column was in the hands of the science editor!