For fuel injected engines it is a different story as you must have a central collector tank in order to have a both setting even in high wing aircraft.
The GA8 (IO-520) has a neat system where the two wing tanks feed to a collector tank via float valves in the collector tank. The float valve for the left tank is located on the right side of the collector tank and vice versa. If you happen to fly out of balance, or if the aircraft is loaded out of balance (fuel or cargo), it's the low tank which drains first, effectively restoring the balance all by itself. Furthermore, this system prevents fuel from flowing from one tank to another while refueling or parking on a slope. So there's no need for a L/R/B/O switch. There's just a firewall fuel-cutoff switch.
Placing the fuel selector to left will not stop fuel moving from the right tank to the left tank via the vent line and then overboard out the vent, if the aircraft is parked on a slope with the left wing down.
In the GA8 all tank vents come together in a plenum on top of the wing, and the exposed ends are so high that there's no chance at all that fuel drains from one tank to the other via the vent lines, even on extreme slopes.
All in all a clever and completely foolproof setup. The only mistake you can make is to fly deliberately out of balance, with the fullest tank on the high side, to restore the fuel balance that way. That will just work counterproductive.