There is a work around so that you will be shown offline when you log out from all devices.
1. Sign in to your account in the Skype application in a computer or a laptop.
2. Select any contact then type this to the message box: /showplaces then hit on send.
The /showplaces command will show the instances where you are currently logged in at that time.
3. Now type this command: /remotelogout then hit on send. It will automatically log you out from your mobile devices, tablet, other laptop except on the one that you are using right now.
Lastly, all you need is to sign out from the Skype application on the computer that you are using and ask a friend if you show as Offline. This one really works. Believe me