That article is a dramatic re-enactment of the ONE person recorded in recent history with that reaction. It has never been observed in anyone else, and he was consuming 3 QUARTS A DAY of soy milk.
For reference, that’s the equivalent of TWELVE cups. Far beyond what any reasonable intake of any food should be.
If you’re a man drinking 12 cups of milk daily, you’ll probably get kidney stones from calcium intake, among other problems.
Currently, research points to keeping intake somewhere below 5 servings a day to both receive the benefits of soy and to avoid any negative side effects.
For soy flour, one serving is 30 g or a quarter cup. So under 150 g a day is considered to be fine and has so far had no observable negative side effects on adults.
So the 6 g of lecithin in soylent is perfectly fine.