Its not part of the OS so why would it affect the Graphene OS license? Its an app, not a library.

The preinstalled apps are part of the OS.

That cannot be true, when I install e.g., Ubuntu system, there are plenty of applications installed for me, with incompatible licenses.

Can you please elaborate on what you mean?

Ubuntu does not aim to be a permissively-licensed system. It can include copyleft (e.g. GPL) and permissive (e.g. MIT) without issue.

Permissively-licensed systems like FreeBSD and GrapheneOS cannot include GPL code if they want to remain permissive.

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IANAL, but I would expect that to fall under "mere aggregation"