TitanMPro on stock, you may be using Google's network location service which helps for when you're indoors and GNSS isn't working.
If you're outdoors and have a clear view of the sky, GNSS will work and you don't need to rely on network location.
If you want to use Google's network location on GrapheneOS, you can follow https://grapheneos.org/usage#sandboxed-google-play-configuration
In the near future, GrapheneOS will be getting it's own initial implementation of a network location service.