Hello not sure if this is an answer but I am assuming you are comparing between an apk built locally vs an apk built using EAS?

From my understanding, if you build your app locally (eg expo run:android), the debug.keystore will be automatically generated and used. However, if you decide to use EAS to build your app (eas build), they will prompt you to generate credentials if you haven't and will manage the credentials for you (link).

That said, this is assuming you do not send the android folder to EAS servers when running eas build, as EAS will generate the android folder using expo prebuild. If you do include the android folder with debug.keystore inside when building using EAS, I am not sure if debug.keystore will be used.

In the expo docs here, it mentions that they have to inject "signing configuration into your build.gradle" in one of the steps when building using EAS, which I assume is what you see when you run eas credentials.