... from my understanding if one were to claim on it they had to pay for new mounting and balance and a new cert. this sound correct?
Incorrect. With the cert you get a new tire and pay for a 'new' cert on the new tire (if you choose) and the tire disposal fee. You do not pay for mounting and balancing. Same as getting a punctured tire in a repairable area fixed at DT, there's no charge for that no matter where the tire was purchased. That includes removing the tire from the wheel, RMA procedure repair, mounting and balancing.
Normally I do not purchase the certs because 'ime' DT is excellent about honoring roadhazard replacement as part of the prorated tire treadwear warranty. I've even had them do it that on two OE tires. Got a new tire at an adjusted/prorated price. With the prorated replacment one does pay for mounting and balancing of the tire.
I did purchase the certs on a current set of RT43s that I needed to purchase outside of a promotional period. I included them as part of the negotiation on the total price. I used a cert on one tire that got an industrial type staple in the sidewall. The procedure was as described.