Default connections made by GrapheneOS are documented at https://grapheneos.org/faq#default-connections (https://grapheneos.org/faq#default-connections) including Qualcomm PSDS (XTRA) for 4th/5th gen Pixels.
On 6th/7th gen Pixels, GrapheneOS only uses GrapheneOS services by default since we use our own PSDS cache for Broadcom GNSS (GPS, etc.).