UPDATE: ok, you need to set a variable before the user task (like in a script task or anything), and then it will complain about any of those fields that are not in the form. however, in MUI forms, it says "[form] must NOT have additional properties" so that is much clearer than the nothing we get with carbon, so it is much less of an issue.
if you have a json schema with this property, make sure it doesn't generate errors.
this works:
UPDATE: ok, you need to set a variable before the user task (like in a script task or anything), and then it will complain about any of those fields that are not in the form. however, in MUI forms, it says "[form] must NOT have additional properties" so that is much clearer than the nothing we get with carbon, so it is much less of an issue.