Earbuds auto detect a bluetooth signal and trys to connect to that signal but also need permission to do so they will auto connect to a device that's been previously connected to I'm pretty sure the phone itself knows if the unique signal from your earbuds have been connected before by saving a sample of the earbuds signal so after the first connection is made it knows to accept the earbuds pairing request without you saying to do so
Thank you for reaching out. I can certainly understand the importance of knowing how to properly connect your Galaxy Buds. You’ll be able to hear everything on your devices with your versatile Galaxy Buds series earbuds. You can connect them to your phone, tablet, watch, TV, and more to stream music, control calls, and enjoy uninterrupted sound when going for a run. Furthermore, you can also switch the connection between other devices in your home using the Galaxy Wearable app or Bluetooth settings. Give this guide a try for steps to properly connect your buds: https://www.samsung.com/us/support/answer/ANS00086702/
