I don't know the reasoning behind why they stop running the street cars and start running the race cars. If it's a time based thing (swapping every 15 minutes to the other group of cars) then it's going to happen the way you see it happening (more street cars than race cars equal fewer runs for street cars and more runs for race cars).
They should've black flagged the vega, not sure why they didn't.
What i've seen in the past is they swap the lanes back and forth, they'll generally run out the Pro lanes (race cars) as it doesn't take very long), then they'll run the street cars for a while until there is a decent line in the Race cars again and then switch. Only times I see this change are when they're running the quick 8.

Don't know what to tell you, and I understand your point just fine.