BlueTracker

Yes, it’ll reduce every instance of it by 0.6s.

We're speeding up minion triggers across the whole game ("Whenever"/"After", Poisonous, Lifesteal, etc. etc.) in an upcoming patch to better match the cadence of Battlegrounds (they'll resolve in 0.2s (down from 0.8s) except for the special cases we flag for 0s). This is done and checked in, just hasn't gone live yet because it requires a full patch.

I'm pretty hyped about this, mainly because a lot of people have wanted things like this and that I think/hope is going to be a really really nice change to the game. But also because (as your title says) Battlegrounds paved the way for this change, and it's cool seeing a new game mode have these positive ripple effects across the rest of the game.:)

Not the last change we're looking to make in this vein by a long shot, but that's the upcoming, completed one.