I've managed a lot of projects in my life and have dealt with people making and then living up to, (more often not) those estimates of duration. I have found some people better at making and living up to estimates and some worse. Usually, those who live up to their estimates are not better at making them, just more dedicated to completing them within the time they estimated.
I once worked with an excellent woman who lived up to all her estimates. This was rare, but what made it rarer was the estimates she provided. She would be in the same room as the rest of the team making their duration estimates but when others would say a task took five, ten or fifteen days, her estimates were always six, twelve or eighteen; always some multiple of six.
I initially suspected that by giving herself an extra day of buffer she was more able to meet her deadlines but, after looking carefully around the room one day, I thought there might be a deeper-seated reason for her strange estimates. It took me a few years before I was able to verify my suspicions but finally, at a company picnic, I caught her unawares with her gloves off.