On modern Android you also need user credentials for OEM unlock; the user needs to enable the developer options menu and allow unlock from there, otherwise the fastboot step won't succeed. (Notably, this preserves the effectiveness of FRP; even "wiping" the hardware and restoring the stock OS install won't allow unlock unless the existing user is verified). But a successful unlock still wipes all data, same as in previous Android versions where the user-side step was not needed.