create two metadata schemas. add them fields with the same names.
create a new folder.
add the first metadata schema, provide some value, save.
open properties for a folder, select the second metadata.
you'll see that provided value is remembered from previous metadata schema.
also when you try to save properties with added second metadata schema you'll get an error:
XML validation error. Reason: The element 'Metadata' in namespace 'uuid:3abc66ed-7514-4e40-8342-cc6cb0e87896' has invalid child element 'NewField1' in namespace 'uuid:a70c31f9-b012-4909-98fd-4c9b0ed3dda2'. List of possible elements expected: 'NewField1' in namespace 'uuid:3abc66ed-7514-4e40-8342-cc6cb0e87896'.