You can induce precocity by grafting seedlings onto mature rootstock. Combine this with cold weather stimulus and you can get very young ~2 year old seedlings to bloom.
Here’s an Orange Sherbet seedling that was about 1-2 years old from seed and I grafted it onto my Bonsai double rootstock tree and it flowered this year, same year the rootstock flowered for the first time
And here’s my NDM seedling. Two sprouts were left to grow together and only one sprout flowered.
Simon