Okay, so lemme break this down real simple

(Correction from prior statement)

GmsCompat is a layer that runs the official google play services and store in the app sandbox which also strips it of all privileges and teaches it to function with only the bare minimum.

The app itself is sandboxed

But it is taught to run without the app panicking

The app sandbox is an OS feature: https://source.android.com/docs/security/app-sandbox.