But this apparently is correct! First, though, his ad is wrong, obviously, in that he calls it a Custom Cruiser. But if you check the 1976 Oldsmobile Brochure, in the section where the Cutlass-based wagons are described, you discover that, yes, there was a "Vista" Cruiser available, but all getting a "Vista Cruiser" meant that year was that you were getting wood-grain siding. There was no actual roof-mounted window. It was the same for '77, the last year of that body style for the Cutlass-sized Oldsmobiles. From what I can tell in looking at the Olds brochures for these model years, '75 was the last year that a Vista Cruiser actually came with what Olds called the "Vista-Vent Roof." Seems kind of silly to call it a Vista Cruiser if it didn't have some kind of roof-mounted window, but that's apparently what Olds did for '76 and '77. Here's the relevant page from the '76 Olds Mid-Size and Compact Car brochure. Note what it says a the far right side at the very bottom as it's describing the features shown in the various numbered boxes: "5. "Vista Cruiser: The elegant Olds wagon with wood-grain vinyl trim." No mention of a roof-mounted window anywhere. Models that did not have wood-grain siding were called "Cutlass Supreme Cruiser."
When this version of the 'Vista Cruiser' first came out in '73, it did have the 'Vista Roof' standard - the 'Vista Roof' simply being a flip-up glass roof panel in a metal frame. It wasn't even retractable.
It does look like based on Olds ads after 1975, the Vista Cruiser pop-up sunroof was never again mentioned.