I think this is particularly notable for actors and actresses like Afshan Azad, who stopped acting on the big screen after her stint in Harry Potter.
Though I think the really huge rude awakening will come when the likes of Rupert Grint, Emma Watson and Daniel Radcliffe are all old enough to play the Harry Potter and the Cursed Child versions of their characters, with kids who are old enough to also go on their own adventures.
At that point, I think the age of former child stars is certainly going to more deeply set in.