Well actually, if you think about it, there are now more Ys games that you jump in than there are ones that you don't
Ys games you jump in: 3, 5, 6, Oath, Origin
Ys games you don't jump in: 1, 2, 4(x2)
Therefore, 5 games in you jump in, 4 games you don't.
Ys 4 counts twice cus Mask and Dawn are completely different. Same with 3 and Oath. I don't count Ys Eternal different though cus it's still basically the same game.