Just because it is currently not done does not mean it is a bad idea. I’d say having travel time makes it more likely for projectiles to be in the spammy nature since you can’t know if it is coming, unlike hitscan who leaves a marker immediately and can just be unlucky moving somewhere the other person decided to guess and throw at. Now should a good read where a player might appear be completely negated, no. But should it do the full damage, I’d argue also know. There can be a healthy middle ground.
Kiriko has a decent fire rate on her kunai. As such I don’t think it is unfair to say that at long range, the damage can be slightly reduced. This will not affect her at the ranges she is supposed to be effective and keep it as a skill shot to deal with people coming for you or have an impact during the team fight.