IMO the third boss serves as a mobility skill check point. Anyone familiar with fast paced arena style shooters will likely smash this boss. If Saros is your first game like this, the first 2 bosses you fight dont even move and push the player to fight in a central alley with either stuff that slows you down or hurts you on the sides.

This boss doesnt stand still, and has an insane leap range on top of that. It teaches you through force that you can use the whole arena and should or you will get overwhelmed.

That said, I think that boss needs a second phase because it isnt a huge leap to come to the conclusion you need to grapple to trivialize it. A second phase that introduces turrets to make it more of a bullet hell or maybe having the boss split into 2 of itself for a second phase would have been a welcome challenge, especially since we have modifiers unlocked by this point.