Adding gypsum is to make the proteins in the tofu coagulate

To make the tofu solid

It is equivalent to the salt precipitation phenomenon learned in chemistry

Adding gypsum of course, there is no harm

The gypsum added is edible gypsum

But some unscrupulous vendors usually use industrial gypsum or hospital waste medical gypsum

This will have adverse effects on people eating it. can have a negative effect on people who eat it.