That's untrue. The main focus of GrapheneOS has always been privacy. This level of privacy is enabled through good security. GrapheneOS goes above and beyond in regards to privacy. No other custom Android OS hosts its own time server, proxies for PSDS and SUPL, captive portal, Wi-Fi positioning proxy, Widevine provisioning proxy, etc.

GrapheneOS doesn't make any connections to Google or Qualcomm by default, unlike all the other other Android-based systems. https://grapheneos.org/faq#default-connections

See https://eylenburg.github.io/android_comparison.htm

As previously mentioned, GrapheneOS hosts a proxy for the Qualcomm SUPL service. In addition, it removes unique device identifiers from the requests, that would normally be present.

GrapheneOS supports the Pixel tool for provisioning eSIMs, but it's fully sandboxed and doesn't share any data with Google.