No. Our policy, subject to the policy terms and conditions, reimburses you for the amounts that are taken by your car hire company from your credit card. In the event of an excess deduction by your car hire company you need to ensure that you collect all the documents and evidence as described in our Policy wording. When you return home you can reclaim the excess deductions from us.
They may still try and sell you their additional excess waiver policy, but you may simply decline as you are covered. The coverage is between ReduceMyExcess and yourself and so the car rental company does not need to approve it.