Randomly remembering past infatuations:
I just thought of this.
Colonnade Cutlasses with opera windows gave you the waterfall.
Colonnade Regal/Century with opera windows gave you a very formal, almost more full-size Buick model's grille if the Regal and gave you a sportier canted grille if a Century.
I know the Regal S/R was the answer to the Cutlass Salon, but I believe they sometimes put in fancy bucket seats or ultra plush 60-40 cloth seats in Centuries with opera windows. I'm not entirely sure, but I have seen a few Century coupes that were NOT spartan. (The Century Special was their $3,999 blue light special.) What was funny is that, if you ever came across a V6 for sale and turned the ignition key, it would fart ... unevenly.
I am taking a random walk down Memory Lane as opposed to a random walk down Wall Street.