pxlkng hi, nice to see you back. Since you brought it up, I have to tell you that regardless of the security reasons there is a very valid reason for using Aurora Store for obtaining apps. I will tell you from my example.
There are several apps available in Play Store that I am using, some tools are completely offline and some have network access and I am logged in with them and I don't mind Google knows it's me because of the functionality they provide. But because the other apps can't talk to Play services which would know from the list of installed apps what other apps I am using and would otherwise provide means and APIs for talking to them possible including some FOSS apps (worth pointing out some apps from Github,, even Accrescent) that contain Google libraries which I want to avoid. Standard stock Android with all encompassing Play services (and other services added on) is designed to do just that.
Yes, using sandboxed Play services is arguably more private because of specific hardening GrapheneOS provides, but not private enough because it is capable to look over all my installs not only the ones I otherwise give it access to only via apps that contain Google libraries and can use network.
Before you go on to say that any app can potentially talk to another app via IPC, let me tell you that I don't believe that ALL apps work this way but stock Android is designed to do just that via Play services.
Many of us who dedicated time to go over official recommendations
https://grapheneos.org/usage#sandboxed-google-play
are aware of it but at the end of the day, it is up to everyone how they decide to source their apps as long as they can verify they are genuine.