The in-game HUD (the enemy heath bar and seed counter), scales not stretches as the size change is uniform. Scaling is not a flaw.
Except when it does not keep the original aspect ratio. Which is what is happening in the non-16:9 widescreen shots.
They are in the original aspect ratio. They're uniformed scaled, they are not stretched or compressed out of shape. Here I took MobsterOO7's 4:3 shot, I uniformly resized it to the same width at the 16:9 shot (so the resultant size was 800x600) and pasted it in on the 16:9 shot for comparison. Apart from some minor fuzziness due to the scaling interpolation, you can see they're the same aspect.
Note I am talking specifically about the health bar and seed indicator that appears when in the main 3D portion of the game, not the full 2D screens which obviously are stretched out of aspect.
I actually had this discussion with others here about this a while back. It is basically a six of one situation (Hor compression vs. Vert stretching). Using stretching is more consistent with the site and seems less confusing then telling people the game is overcompensating for an aspect ratio that is not as wide as 16:9.
I just think it's worth making a distinction that the screens were made for 16:9 and it's actually thinner aspects that are incorrect. The connotation of "stretching" is that the screens were designed for 4:3 and are strechted to fit wider screens, this is not the case.