It's really pretty difficult to tell much of ANYTHING from a 7 second clip of a 7+ minute lap. It's intended to stir the hearts of those truly enthused. Those who aren't enthused will not likely be impressed, one way or the other, by this clip.
In the earlier clip, the Z/28 pilot was "on it", the ZL1 not so much.
And 3 seconds at Milford means 3 seconds at Milford, on a 1:30 lap. It doesn't necessarily mean 15 seconds at the Ring. Although it might.
"Time" will tell.
So be it.