Yes, it is correct to say that both (Bryan and Cathy) think they are not the same.
Example: Bryan, Cathy, and two friends are out having a soda (pop, a soft drink), some having Pepsi and some having Coke.
The friends talk about the tastes of Pepsi and Coke. "This one tastes more lemony", "this one tastes more sweet", "this one bubbles differently", "this one isn't overly sweet."
Bryan: But they are not the same then.
Cathy: No they aren´t.
Bryan and Cathy agree that Pepsi and Coke are not the same.