For game assets is it ok to intentionally stretch UVs, or does this interfere with pixels per units? I have a question about texture stretching and environment design, and was hoping a Blender/asset creator guru/environment artist could give me some answers. I was reading about something games use called "pixels per units", which is apparently supposed to optimize a game. I'm not sure how.

In the following screenshot, I've been stretching a sci fi object's UVs to better fit the texture details. Is this bad? It certainly breaks the pixels per units rule, or is this a common practice? I've noticed this sort of thing in AAA titles, where they stretch or squish UVs to use a single texture in a variety of ways. But is this discouraged or not optimal?
Just a curious thought. I can't seem to find an answer online about intentionally stretching/squishing UVs to fit a texture.
I don't think there's anything wrong with stretching UV's from a technical perspective, it might even be desirable. 

The main thing is that from an aesthetic standpoint it looks good. I would say that as long as it looks good, and is not giving you a blurred or pixellated effect (unless that's what you want), then you should be fine.