E24 Is there much privacy lost in doing this?
Not really. "Sensitive data is stored in user profiles. User profiles each have their own unique, randomly generated disk encryption key and their own unique key encryption key is used to encrypt it. The owner profile does not have access to the data in other profiles. Using a secondary profile for regular usage allows you to make use of the device without decrypting the data in your regular usage profile. It also allows putting it at rest without rebooting the device. Even if you use the same passphrase for multiple profiles, each of those profiles still ends up with a unique key encryption key and a compromise of the OS while one of them is active won't leak the passphrase. The advantage to using separate passphrases is in case an attacker records you entering it."
https://grapheneos.org/faq#encryption