If someone grows a new tree from seeds after buying your fruit, their trees will take several years to bear fruit right? Works almost like a patent anyway.
(I don't know fruit growing well so maybe that's not true)
Again, not an expert, but I believe you need to graft a cutting from a tree that already bears fruit onto rootstock. Only the inventor of the new seed variety would have a fruiting tree.
You graft a bit from a small tree, to a much more mature rootstock, so the time to market is a lot of less than trying to grow a small tree from start. So like 1-2 years instead of 10+ years. Yes, you still need to get the scion from someone that has them because apples don't breed true, the only true one is the original that all the others are grafted off of.