getDefaultFormState includeUndefinedValues

[dieseldjango]

I'm looking into #2708, which involves pruning empty nested objects from the form data before submitting for validation. There's a includeUndefinedValues parameter to the getDefaultFormState() function that is set to true only when getting data to validate. This seems to ensure that all properties are created in the data with undefined values, rather than just leaving them off.

I'm sure it was put there for a reason, but I don't get why this is necessary. Obviously for what I'm doing I want to do basically the opposite - leave empty values off of the data when validating. Can any one shed some light on this?