They consider it a fire hazard here and just about all of them make a stink about the practice. But I'm sure every state is a little different though.
It may be a state to state issue. My DH and I have filled up both gas tanks at the same time. Nobody ever said anything to us.
7% with 2X fuel points and 14% on 4X fuel points sound right, assuming you use the entire 35 gallons. Both my DH and my cars have smaller gas tanks. We don't even come close to 35 gallons. And now, my DH's employer pays for his gas. And will pay for his first tankful on our upcoming trip to Disney. So if we're lucky, we may use about 12 gallons. That's 5% for 4X fuel points; same as Target.
You also have to ensure you can fill up your gas tanks at least four times within the time period. Fuel points are only valid through the end of the next calendar month. I still have over 800 points I have to use by the end of October, and I have no idea how they will be used. I want to fill up at a Kroger fuel center on the road; however I don't think there are any fuel centers between Knoxville and Dalton, GA (about 130 miles). Knoxville is too close, and I think Dalton would be too far. I'll probably just fill up the other car's tank tonight, even though it has a half tank of gas.
In a nutshell, Krogers, with 4X fuel points, is much better than Target as long as you have a larger gas tank or can fill up multiple cars. Else, you may be better sticking with Target.
ETA: Krogers will probably start their 4X points sale in about 2-3 weeks. They usually run a month; from the second or third week of November through the second week of December. At least, it was that way in past years.