So here's what we've found:
- So if your form is empty and then you add content to a blank form, it actually obey's the ui:emptyValue value
- If your form is passed data when you view it, e.g you're editing data then the JSON schema form doesn't really understand how to utilize the ui:emptyValue value. This is especially true if your data store returns null data.
Work Around:
I was able to add a transformer to my database request that changed it fields from null to undefined. Once changed to undefined, even when editing data it would properly follow the ui:emptyValue value on validation