Since Android 9 more and more core components can be updated by Google by the Google Play System Updates (GPSU) that come from Project Mainline (https://www.xda-developers.com/android-project-mainline-modules-explanation/)
Do you know how long Google will provides these updates? I hope that there will be updates even after the phone manufactures have stopped providing the "normal" android (security) updates. If this is the case the updates of the phone manufactures would be less important since you get important updates directly from Google.