Thanks for sharing @starfruit
yes, it is true that a great number of grafted jujus will produce on year of planting/grafting as pertained to in the links
was hoping though the links explicitly mention of jujus grown from seed. The links alluded to trees of named cultivars. That they are already named or referred to as trees indicate they were not grown from seed, but from grafts. Also, 50% to 95% of the trees being productive on same year as planting insinuates that those were grafted trees.
50% chance producing the same year is a bit too high for juju seedlings, so 95% would be miraculous, but of course i myself wish am wrong, and will actually throw a party if proven wrong 
from my findings, would say only 2% of my seedlings did that, at least here in vegas. I can safely say have grown at least 2000 seedlings over several years
your tree is probably a li or lang. You can graft some honey jar and sugarcane scion wood to your tree. Those are the two most readily available ones that are favored for juiciness