The results from such a test can wary widely depending on how it's done and what sort of movement there is on screen.
One of the more obvious cases where high frame-rate is of benefit in DCS is when using head tracking such as TrackIR, which is much smoother and more responsive at higher frame-rates. Personally I prefer it to never drop below 75fps when using TrackIR on my 144hz monitor. The TrackIR itself runs at 120fps.
On the other hand, if you are just staring at a scene with a static camera and a vehicle driving by 100m in front of you, there is very little actual movement happening in the image, so 35fps could look perfectly smooth under these circumstances.
So you see, it all depends on a lot of factors! I'm absolutely certain I could come up with a test where anyone would be able to distinguish 60fps from 120fps. Actually, I've done blind tests like that on friends and family, and they can always spot the differences, and end up looking really surprised afterwards, but it's all about coming up with a test where the difference is obvious. I could make it very difficult if I wanted, but what's the point in that? The point is that the human eye can definitely surpass common monitor refresh rates when there's ample movement on the screen. There's a lot of people feeding the old myth that "the eye cant see more than 30fps" but they are wrong and it's easy to prove it. In reality, our eyes are not digital, so it's actually impossible to say where the limit is. I'd say it's infinite, but of course there's also diminishing returns.