Just so we're on the same page..
Lets say the corner we are talking about is a left hander. So you, the driver, are sitting on the high side of this bank, doing circa 200km/hr. Which way side of the tank is it that you think the fuel is being pushed to?
Gravity is trying to pull the fuel down to the left side of the tank. That's where it would be sitting if your car were parked still on that slope facing the direction of the corner.
When you are turning hard left on the FLAT bit of road, the fuel makes its way to the right side of the tank.. agreed?
On the bank, while turning left at 200-250km/hr, the fuel will 'climb' back up to be approximately flat on the bottom of the tank - negating the force of gravity pulling it down. Yes, of course it won't be 'perfectly flat', but its not perfectly flat doing 200km/hr on the flat straight bit of road either. (but I didn't say 'perfectly' to begin with) Also it will vary depending on whether you are doing 180km/hr or 220km/hr, so lets not split hairs. If 200 happens to be the sweet spot, then the differences will only be like taking that corner at 20-40km/hr.. ie, not nearly as much fuel movement as you think. Hence just not a good example for what you were trying to say. That is all.
Grab that bucket from the laundry, put 3 inches of water in it. Go outside (that's an important step), hold the bucket out at an angle and start to rotate - watch what happens and get back to us.
also! Make sure you get someone to take video - not for any scientific value - I just think it will be amusing when you stop.
Remember this is why the corner is banked the first place, to negate the lateral G forces - on the tyres mostly - but same result for the fuel.