Glucono delta lactone is really common nowadays in mass production, you take a look at hmart (https://fresh.hmart.com/meat-seafood-produce/dairy/egg-tofu https:

Glucono delta lactone is really common nowadays in mass production, you take a look at hmart (https://fresh.hmart.com/meat-seafood-produce/dairy/egg-tofu https://fresh.hmart.com/meat-seafood-produce/dairy/egg-tofu), and calcium sulfate is often add with it to beat down the sour. As I know both of the chemicals you mentioned are used in traditional Chinese tofu making, and they are still in market. Somehow, they require a lot trials to get it right, so for nonserious stuff, glucono delta lactone is easier. Also my guess about the traditional way is hard is that is all related to the water hardness and other ions in water