I remember that my wife once bought an over the counter cold drug in Italy that had > 1g per pill.
So we should be aware that it's very easy to overdose this particular drug.
I was surprised it was that low, but I think you misread/misremembered. From your link:
> Toxicity is likely to develop in adults at:
>12 g over a 24 hours, or 7.5 to 10 g in a single dose, or Doses 350mg/kg
The 4g/day is the dosage threshold, but it seems they set it to 1/3 of the toxicity threshold.
This is also a bit misleading, it’s the most common cause of acute liver failure which is overall quite rare in developed countries. The most common need for transplants are still by far progressive chronic liver diseases leading to cirrhosis.