Flew LAX - CGK (via HKG) last week and nobody asked to see that I had downloaded the app at any step in the process. Hell, I don't think anybody even checked vaccine status (unless they did it when I wasn't paying attention). Got my eVisa before leaving for the trip, so sailed through immigration. Did my customs form online a couple of days beforehand, so breezed through customs with a scan of the QR code. Super-easy.