The legal advisory firm Vermogensmonitor warns against this. They believe that it is too easy to object to the WOZ score and that the risks are not always clear enough.
In many cases, having a high WOZ score is actually beneficial as you may qualify for lower mortgage rates.
On the other hand, you pay more local taxes and the notional rental value is higher.
A homeowner who successfully protested his high WOZ rating in 2004. He managed to cut the estimated value almost in half. After about a year, his mortgage provider also found out about this and imposed a substantial risk premium on him.
With the present WOZ decision it is actually possible to negotiate an adjustment of the tariff class with other banks, which can lead to considerably lower monthly costs.
Most mortgage lenders do not automatically lower interest rates when the home value increases relative to the mortgage by making repayments or adding value to the home.