The pump is in its own bucket that it fills when running, so it's always submerged regardless of the fuel level in the tank. Been this way for decades.
Another myth is letting it run low makes it suck up trash from the bottom of the tank. The pump pulls from the bottom of the tank at all times.
However, I would suggest, especially with an older/higher-mileage pump module, to keep it above ~1/8 tank. The level sensors commonly go bad and read the level inaccurately, making the gauge show more or less than what you actually have in the tank. If it sputters during a moderate acceleration and your gauge still shows to have enough fuel to not trigger the low fuel warning, then it's likely reading inaccurately and you actually are on fumes.