Yet more Minty errata: G3 pegasai can fold their wings, albeit not to a comfortable position · 7:34pm Feb 3rd, 2018
Straight from the G3 books:
Here's contextually male (there was a spelling/continuity mistake in the original book) Star Catcher folding her wings as she talks to Twinkle Twirl:
So it looks like I was wrong when I said that the G3 ponies can't fold their wings at all, but it DOES look like they can't fold them to their sides for comfortable sleep al-la G1 or G4.
EDIT:
And here's a couple of examples from G1, and G4: