Self casting when hovering over an ally makes the ability go onto the ally instead

I rarely play a support champions with point and click targetable shield/ heals but I use I use smart self cast when I do. However I have noticed that if I just happen to be hovering over an ally the shield will go to them instead of onto myself. This has been happening for years, but I don't play supports often enough to remember.

This is incredibly annoying and it happens quite often, especially in clustered team fights (aram is a nightmare). I'm able to re-create this with a 100% success rate on every champion and with multiple key bindings. I'm really not sure why this is a feature.. it seems more like a bug.

I really wish there was a way to make it so when you self cast it is 100% SELF cast, no matter what you are hovering on.