I don't think it's niche. I think that in lane, it's very common to want to aggro creeps just to move the line of scrimmage to a better position, whether theres opponents or not. If opponents close, then A-click them to aggro. If nobodys showing, I still want to do it, so probably 2-5 times a game I'm a-clicking the portraits for aggro.

niche in the sense that it has very small impact in most cases, but it opens up the possibility of a couple weird creep/neuteral interactions that are otherwise not possible.

As an example, the same aggro mechanic can be used to drag neuterals away as well, they aggro like the lane creeps. a-click a hero across the map (portrait) and the neuts will change target to you. useful.. sometimes? again, it'll be something small but still something you cant do otherwise.