While they have inproved the chin straps, the all velvet hats are still very much made. Many Event riders at the lower levels use them for dressage before switching to skull caps. It's possible that it's a recent picture and she is using an older helmet.
It's not that the chin strap has improved. The chin piece Charlotte is wearing is not used anymore. You won't find a decent helmet with it anywhere, beacause it's unsafe.
I'm not 100% sure but I thought it was forbidden in official competitions.
Those pics are really weird.