Groovy addValidationError method limitation on dashboards?

Summary:

I have a simple groovy rule that runs before save that highlights a cell if a value is not entered. It works just fine when accessing the data form natively but does not within the context of a dashboard grid (single grid dashboard that points to the same form).

When I click save on the dashboard I do get the generic error message but don't get the cell highlighting or error message tool tip on the cells. Is this simply a restriction\limitation of dashboard grids?

Thanks