Is data unrecoverable when deleting Private Space as when deleting profiles?
Yes, it's similar to a user profile especially if you set a dedicated lock method but can be reliably deleted even when sharing the lock method with the Owner user, since it still has separate encryption keys and protection. It shouldn't be possible to get the data when Owner is unlocked but the Private Space is not even when the lock method is the same. Reboot is still best to get data back at rest instead of relying on things being zeroed as they should be.