I don't know if this helps or hurts, but my Rosedust has open wing slots and so does my Hollywood, so it's not strictly a pose thing -- for the US flutters anyway. Also my Forget-Me-Not has ultra-curly hair like your second picture but closed wing slots like your first.
Flutter ponies, man... :shrug:
Rosedust was released with the 2nd set of flutters, along with Lily. So her 2nd set mechanism makes sense, at least. :)
Here we have:
Wind Drifter - open wing tabs. Hair in one long curl.
Lily - closed wing tabs. Hair in one long curl.
Rosedust - open wing tabs. When my gf bought her from a car-boot sale back in the 90s, her hair was faded totally white and also in the most amazing wild corkscrew curls! No idea if they were original or the work of a hairdressing child. Had a photo but can't find it at the moment.
All of them are from the UK.
I found my photos of Rosedust's crazy hair: https://imgur.com/a/ZsjMrhg
https://imgur.com/a/ULfl0Ow
I found my photos of Rosedust's crazy hair: https://imgur.com/a/ZsjMrhg
https://imgur.com/a/ULfl0Ow