>Citation needed. grapheneos themselves sure doesn't understand this
The GrapheneOS team understand full well that in cases where the Play Store does not allow installing an app on your device due to device or georestrictive rules you may have no choice. I have seen them mention this and acknowledge it first hand. What they do not want is for people to become satisfied with subpar solutions instead of striving for bare minimum privacy/security standards. They want a Play Store alternative front end to at least be able to guarantee you are receiving the right app you want instead of being a substitution attack risk. I don't think that is unreasonable.
>The official website has an install guide for google's background services, saying it's fine because it's in their security model.
The context is that before sandboxed-play-services were introduced people were sourcing APKs in unsafe/via unverified routes and having all sorts of problems with app compatibility because since GrapheneOS is a privacy project that do not accept sending copious amounts of data to one party with a mediocre privacy policy they included no Google services at all. sandboxed-play-services is a specific solution to the problem of apps being dependent on Google Mobile Services for functionality, and in that sense it is entirely optional. It was the best way for them to provide compatibility without destroying the privacy of their platform by introducing a privileged Google binary that can glean and abuse your production environment. It's reduced to the same level as any other app the user might choose to install themselves (which GrapheneOS want absolutely no say over as a user freedom protecting project).
GrapheneOS do not bundle any Google services in their official installation. They do not endorse Google's data collection and service practices. They do not believe Google tracking is fine in anyway, and the evidence is here: https://eylenburg.github.io/android_comparison.htm
What they have done is provide a workaround for people who have no alternative, while making sure it does not violate the device owners device in a special way compared to any other app they might install.