When should toilet training begin for young children?

Dear Teacher Q, hello! My son Niuniu is about to turn 2 years old, and he is still wearing diapers. My mother helps me take care of the child every day. She loves cleanliness and is always nagging, saying that when I was a child, she started holding me over the toilet to poop and pee from 6 months old, and by 2 years old I could toilet independently. Now the child is already this big, and it has long been time to start training, and so on. But some parenting-related books I have read say that it is not advisable to train children to use the toilet too early, and attention should be paid to the child's psychological development. Some other parents have told me to let nature take its course, and that diapers should be worn until age three or even longer. Now I am really a bit confused and have no idea what to do...