Stayed up way too late seeing if that hidden quest to get the flower crown was legit, I can now confirm that it is! Dorian’s even prettier now =D
The tldr version:
1. go to The Emerald Graves
2. jump on this tiny rock house 50+ times, doesn’t matter if you fall off
3. get the quest to gather 10 crystal graces, then turn it in
4 go to the secret underground stairwell in Emprise du Lion, the chest will be at the bottom