It is true that a patch is always an update, but an update doesn't always have to be a patch. Let me explain...
A patch is a word used for explaining that a fix for a bug is in the update.
An update only refers to the version number increase of the program (or in this case game). Like the latest update from 1.12 to 1.13.
An update can include various things, patches, new features, reworked/improved features, add-ons and in a closed system like a console's case also drivers for various hardware (example: TH8 RS shifter, new Clubsport stuff... etc).
And that's simply how it is. Now in Kaz's case he always implements patches in every update it seems, but not all updates include any extra things.
Just my opinion. Now just let's wait and see what we'll be getting ^_^