Matched Date field

We've been using the Matched_Dt field from the VOUCHER table to reference when vouchers clear exceptions.  But we've noticed some inconsistencies.  For instance, where the Matched_Dt field is blank but the voucher is matched.  For exceptions cleared via override, this makes sense.  But where there doesn't appear to have been an override, the field is also blank and the voucher matched.  What conditions cause the field to be populated?

Also, is there a way to reference individual match exceptions from history - and when that rule on that voucher line cleared exception?  Doesn't appear to be a like field on the AP_MTCH_EXP_DTL table.  There's a notify date and a creation date field - so no trouble determining when the exception triggers.  But nothing to help us understand when the exception cleared.