So following the documentation here I should be able to disable the allowUpload feature to force authors to use just the Assets:https://docs.adobe.com/docs/en/aem/6-1/develop/components/components-develop.html#Disable%20Upload%2...
I am attempting to do this with TouchUI and not with classic.
I have attempted
in AEM 6.2 allowUpload="false" works in the same way as it works in Classic UI.
Just add this property to the node "file" of sling:resourceType = 'granite/ui/components/foundation/form/fileupload'