There was no G-body designator with a "Cutlass S". Depending on who you believe, there was a story going around that there was Olds's push to make a 1968 Cutlass SS but some fight with Chevy blah blah blah....ended up being a Cutlass S. Better than the base model F-85 and Cutlass, but not as classy as the Supreme, nor as sporty as the 442. I believe it only lasted through the 73 model year, after that they used "Cutlass Salon".
Interestingly, 69 Cutlass S even had a Youngmobile ad showing the car and some pirates around the car sword fighting. In that ad, they mentioned something about "Cutlass, the gay blade" or something of that sort. I got that ad somewhere around here. But you'd never get away with that ad today. PC police would be all over it.
I personally don't subscribe to that Cutlass SS nonsense. These names and such are typically thought up several years in advance and usually, just a name. The "S" is just an "S". Nothing more. Although, in 68 and 69, the Cutlass S and 442 were the only two body styles that could get convertible tops on. In 1970, they used the Supreme body style for convertible.
Some cues of future cars can historically be found up to 7 or 8 years in advance of the next project. Not so much anymore as design times have been cut down somewhat due to *gulp*, dare I say, more efficient "design table to garage" timelines. But sometimes it still takes a while. As I mentioned in another post talking to a GM wheel at the Oshawa Camaro homecoming in 2011- out of the blue he asked me what I thought about a mid-engine Corvette. This was about 8 years before they actually were unleashed. Another worker I knew at the Camaro plant told me of a new hood and induction system they were working on in another hidden part of the plant on a stripped down future version of the Camaro with a big engine in it (turns out later that the car was the 2014 Z/28).
All that to say this- Names come and go. Sometimes they mean something (
Impala, Canyon, Cutlass etc.), sometimes they don't (S, CTS, ATS, etc.)