Maybe the rep meant you could do either/or, not both reservations. If TD is once again not only keeping you at the same time but also the table with the same people each night then you get into the "notify my servers and table mates" mode when you plan to dine elsewhere for the evening. If it's just the "fixed time" then that makes it easier to choose to dine elsewhere and they won't be "holding your table" in the TD MDR, at least not for very long.