So what is wrong with drawing butterflies with this wing position? Nothing! It's possible and looks good.

Depends on whether you're depicting them from straight above or at another angle. The point remains that they don't typically hold their wings that far forward. It's not clear how far forward the one in the picture has its wings because of the angle.

So, sure, if you're depicting a buttery in a completely different pose to the examples in the article, it might be right.

Who can dictate what pose a butterfly should be drawn in?

You're being obtuse. You can draw it however you want if you don't mind depicting ones that look dead.

but you're not.. they can be in that position and some of them are in that position at rest

Maybe some can. I don't know. But the point remains that the supposed "counter example" is not evidence of this, and that irrespective of that, because most butterflies won't have them in that position depicting them like that will make them look like they are likely dead whether they are or not.