I have encountered some people RL and not that think that any child over 18 months should be potty trained. My frind from India said that they train them in India at about 9 months! How, when the nevers between the brain and bladder are not fully developed. I have heard that Europeans think that English people are lazy because their children are toilet trained later.
IMO surely if the child is not ready, no amount of training will work. I tried my 2.8 year old in knickers and sat her on the potty every hour in the summer she did not understand a thing, and gave up after 2 weeks, i tried later in October and put her in knickers and sat her on the potty regularly but while the poo bit was nearly sorted, she had no concept of going for a wee and that she was wet and could not tell you wether she had done a wee or poo despite me perservering for a month and a half. So i put her back in pull ups but still put her on the potty regularly