From the book "The Elements of Eloquence" by Mark Forsyth:

adjectives in English absolutely have to be in this order: opinion-size-age-shape-colour-origin-material-purpose Noun. So you can have a lovely little old rectangular green French silver whittling knife. But if you mess with that word order in the slightest you'll sound like a maniac. It's an odd thing that every English speaker uses that list, but almost none of us could write it out. And as size comes before colour, green great dragons can't exist.

Do generative Natural Language Processing models know this? Have Recurrent Neural Nets been found to learn it?

I love this. :D