I don't think they've made him an adult, per se, they've made him start thinking like one more, which is a part of growing up. And I wouldn't say it's "sudden". They threw Tim Drake into that mindset with what happened to the Obeah Man, and things have been snowballing ever since, with him being forced to grow more in KNIGHTFALL, NO MAN'S LAND, through Young Justice and The Titans, MURDERER and FUGITIVE, and of course, when his father was killed, as well as countless other events. They've been slowly building to this for years now. Making him someone who recognizes his responsibilities more fully. But let's not pretend that Tim Drake hasn't possessed this element for a long, long time.
They should have just called him "Redbreast".