I'm on Android (Google Pixel 2) and I never had issues before... if my phone is asleep, I hit a button to wake it as I approach the car, and there was never a delay...
Until 48.12.1. Now I've twice had the car fail to recognize my phone as a key. Second time, I did some testing - rebooted the car, cycled Bluetooth on my phone, neither helped. Rebooting the phone fixed it. (Both times.)
Don't know if it matters, but I sync the phone with 2 cars and 2 sets of headphones regularly...