Just applying common sense here, it is referring to “a” vehicle that could possibly or has assisted you in your activation. Not to something that simply passes by !
The vicinity part has to be stated cos sometimes a car park or otherwise is within the activation zone. That is not to say it has assisted you greatly, it is within the nature of that zone. Most people would have done it the same way. However if someone explicitly uses a vehicle to go to a activation zone from lets say a public road, then this would be considered cheating as it would be giving that particular activator(s) an unfair advantage over everybody else. This is, from my POV the reason the rule exists.
There are plenty of summits in GW/NW that you can drive up, and I have in other circumstances. But apart from not complying with the program, the sense of achievement is drastically reduced.
The active part of SOTA does not lend well to the disabled or physically unfit, it never will. But chasing does at least give people a chance of taking part.
Jonathan