Not a fancy way of saying GMO. Plants can do a lot of wacky genetic things totally naturally, but keep in mind pretty much any plant we eat has had thousands of years of selective breeding by humans. We've essentially trained all of our domesticated crops, naturally, to be a certain way.

Specially, plants can do some "odd" things when it comes to reproducing and creating fruits. For example, we're familiar with the concept of getting 1 set of genes from our mothers and 1 set from our fathers, they would call this "2N" genetics. In theory plants work the same way but getting 3N, 4N, 5N, etc plants is really common and doesn't hurt them as much as it would us. If you ever see a box of monstrous strawberries at the grocery they probably aren't GMO, they are just 3N or 4N strawberries (natural genetic freaks, not human engineered genetic freaks).

What I'm saying in the above is some plants, if the flowers don't get fertilized will just kill the flower and move on (like apples), other plants will keep the organ alive and produce what's called a "virgin fruit". Since no fertilization occurred the plant can't make normal seeds, but they'll probably still be there. They will just be super small or soft and you eat them without noticing them. Those are the seedless grapes and oranges and stuff per OP's prompt.