Strictly speaking, "unborn victims of violence" are not the victims of abortion. I suspect this bill, like the one passed in the US Congress, refers to unborn babies who die as a result of mothers who are murdered.
Yes, you are right, there will be a number of these cases. But there will also be the cases where the violence or crime committed against a pregnant woman results in miscarrage/death of a fetus but not the death of the mother. Like car accidents where the driver at fault is charged with manslaughter because he/she violated traffic laws or was DUI, and mom lived, but miscarried, etc. Or domestic violence situations where the mom doesn't die, but injuries result in fetal death.
In the past, the death of a fetus could not be used in the charges against the person at fault. This is why this legislation has the leftists up in arms. It comes way too close to abortion.
The significance of the bill is in that it recognizes that the unborn can be a victim.
The Catholic church in Oregon has its priorities badly misplaced.