Regardless, when using an app store you are required to trust the app itself, the party who maintains the app, and the source of the apps. If your source to get the apps is from the same party who develops the app store, there is less parties to trust. It's a big reason we provide the option to install the apps like Markup, Android Auto, or Play Services directly from GrapheneOS as well. You'd only need to trust the apps and the developers rather than an arbitrary additional party just to get those apps specifically.