I use the feature to automatically end a secondary user profile when you leave it. Considering it like turning it off, you wont get notifications from it and it won't run in the background, but it keeps data safer.

I meant that in my own requirements, I am a simple person with not a lot to target for. Some GrapheneOS users may use iPhones for miscellaneous low-risk use like corporate things and use a GrapheneOS phone for other higher-risk activities instead. I own Apple devices but they aren't used in any meaningful ways. iPhones are predominantly a target by sophisticated actors with moderate success, but the scope of who they target is also extremely limited and not a concern for most. GrapheneOS should be a choice for people who could be a victim for that, but obviously GrapheneOS isn't exclusively for them... else I wouldn't be using it.

Don't use them if you can help this. I don't use my number beyond when it is forced to be used like for accounts, although your use case is a lot different to mine so I can't really stop you. Project doesn't recommend using SMS for communications and cellular networks aren't designed with privacy in mind and cannot be fixe, a user using mobile data would usually be aware of the privacy shortcomings and use it anyway, like I do.

The play services on GrapheneOS are unprivileged and only access what you allow them to, and what you do in the Google apps themselves (for example searching an app in Play Store may be in your account activity history somewhere). It appears that way because that's originally designed that way, but a compatibility layer essentially tricks Google Play services into believing it is running with privileged access when it isn't.

You can use an additional user profile to contain the play services and apps dependent on it into just that profile, and allow it to run and share notifications to other profiles to get alerts like texts from a text app you use? This is just a suggestion and it may not fit your use case though.