To be honest I made this fix while doing some other work and I didn't thought too much about the details. Definitely a good point.

Looks like this replaces the cooldown being refreshed when sprite of boomerang returns to player with a timed one. So fixes lot of bugs that can happen if sprite can't reach you or is unloaded. Especially with higher movement speeds/ higher range this means you can have multiple boomerangs out at once now. May be worthwhile to update the patch code to just run at start to avoid this while also fixing the issue.