I would have expected more 3yo fillies to have won the race if that were the case Steve - as it is, I can only see 1 3yo filly having won it in the past 29 years.
Of course, in the 10 years prior to that 8 fillies won - 4 3yos and 4 older. I suspect you might be having a moment of reminiscence in whipping this one out (matron).
The key here is "improving" 3yo fillies. Most 3yos have run their season by Arc time. Not so with Sarafina last year or Galikova this. 11lb is a huge advantage in such circumstances at this time of year when the three-year-olds have gone some way in shortening the gap on the older horses in terms of strength and maturity.