Although the nice thing about Aurora Store is it allows you to install apps without a google account linked to your device, keeping Google Play Services signed-out.

Somewhere in the FAQ GOS advertises that Play Services can be used without signing in, but they also recommend the official Play Store (which requires signing in) and explicitly don't recommend Aurora (which doesn't).

Unless I'm missing something, I don't see how you can functionally use Play Services signed-out when in order to obtain those apps in the first place, you need to sign into a Google Account for Google Play.

That's personally what I used Aurora for, plus as an easy way to export APK files.