Bear in mind, too, that any actual published data represents what the OEM was both able and willing to achieve in test. Once you get any of the VMCs low enough that they don't affect performance, there's no incentive to keep pushing to see if you can break something; you take what you've got and call it a day.
So you can't infer a great deal about the underlying aerodynamic behaviour from the published numbers. Maybe the 'real' VMCA on the A320 IS affected by flap position, but Airbus didn't need to find out to get decent numbers.
(I know of at least one case of ours where we chose to publish a single VMCA value for two flap configs, even though the 'real' data show a slight difference. We just use the higher, conservative, value for simplicity.)