One of the things that puzzled me about this was that it worked differently for different grafts, The Pear + Lemon -> Plantain always yielded Plantains. Apple + Cherry -> Pomegranate rarely yielded Cherries and never yielded Pomegranates.
Plantains are a common fruit. Cherries are Uncommon. Pomegranates are rare. That has seemed to be the limiting factor in every graft I've done. I thought that if I grafted a rare to rare plant, it might work. But when I grafted a Pomegranate to a Growfruit tree (both are rare fruits), I still never got a Pomegranate.
Grafting is less useful, but at least knowing this saves you from beating your head against the wall. And it might make the approach to EA a little different. I can live with getting only 1 Dragonfruit from a spliced plant. But the percentage chance for rare fruit must be higher. Because I haven't got any rare plants from any of the grafts I've done.
This makes all the old grafts that would produce rare fruits (or flowers) kind of pointless. But grafting common plants will still yield decent results. So if you want year-round tomatoes, you can splice them with Sage and get a steady supply. Or if you want to build a greenhouse, at least you can consolidate things so it doesn't have to be so big. Just understand that you will want to graft common plants to uncommon or rare plants. Because if the second plant is uncommon you will get very few fruits or flowers. If it's rare, you will get none.