I have an update on this, using Xcode 16.1 (posting this for my own purposes - I'm sure I'll find my way here again!)

1. Figure out the Device Id by going to Devices and Simulators in Xcode, finding the simulator in question, and looking at the 'Identifier' field
2. Go to ~/Library/Developer/CoreSimulator/Devices/<Device Id>
3. Delete the data folder
4. Erase all Contents and Settings... should now work 🤞