Vi Not Following Kass?

I'm not sure this is a bug but it seems really weird for me to NOT follow Kass if he Rs at a certain time. The damage still goes off and he gets knocked up but I'm on the other side of the screen and I'm getting nothing from the Aftershock damage because he's not near me. I assume this may be similar with Ezreal too. I don't think this makes all that much sense.