Oh no, not at all. Zorin Pro comes with Zorin OS Pro Lite. 
Lite is still in development for Zorin OS 16, but you will get a notification and a download link from ZorinGroup once it is released.
That being said... You can have it all, right now, if you want.
We can install the XFCE4 desktop on your system and get you all configured-- that way when Zorin OS 16 Lite is released, you need only add the Zorin Desktop portions. If you are interested, I can walk you through the process.
The forums are often a great go-to source for help and information.