I've definitely eaten fruit off seedlings that was pretty much identical to the parent trees. They don't take too long to reach maturity and start producing, given good growing conditions.

BTW, I have about 5 tiny seedlings growing right now, and looking to plant 20 more after harvesting my sister's tree in the next few weeks.

I wonder what method is used for grafting nursery stock? hmmm...lemme have a look

Loquats will spread like weeds and the ones grown from seeds will be just like the parent tree.