In terms of evidence of people leaving HK. I applied for my 2 kids to join a very highly regarded international school for the next school year that normally has long waiting lists and needs parents to register their kids at birth.
It took 11 days between applying to have the assessments and getting an offer (offer came hours after the assessment). Of course, I’m delighted for my kids, but this also paints a very worrying picture of the expat exodus in HK.