Al, you seem to be equating "vehicular" with technically legal.
One of the common misconceptions about VC noted in the Wikipedia article on vehicular cycling is, "VC means you have to follow the letter of the law"
In the context of understanding vehicular cycling, one must comprehend the subtle but significant difference between cycling on roadways in accordance to the vehicular rules of the road (which is VC), and cycling on roadways in accordance to the vehicular laws of the road (which is not necessarily VC). Sometimes this important distinction is missed and VC misunderstood as a result.
Vehicular cycling requires judgment, not blind following of the letter of the law.
Anyway, I agree that according to the letter of the law, each cyclist is operating an individual vehicle. But the point of this thread is how should things be.
I will say that trying to adopt this in law would be very difficult. Even in the artificial and controlled environment of a bike race, it's hard enough, where judges decide whether a given gap is sufficient to warrant separate treatment in terms of assigning who gets what time at the finish line.
On our ride we have climbs, and lights on climbs. On climbs gaps start to develop, and what often happens is a light will switch when the gap is marginal. Some cyclists will proceed, others will yell "stop" and hit the brake. What the right call? Who knows? You're never going to get everyone to make the exact same call about every gap.
Anyway, it would be nice if the law could somehow recognize this, but I don't see how it could. In the mean time, common sense makes the determination, as best as it can.