Robots that specialise in one thing already exist. In big factories, where they'll peel and dice tons of onions per hour, being fed via unsexy conveyor belts into massive dicers.

That's the problem with robots like Optimus. The "specialized" part (Cutting the onions) is 1% of the skills. You'd still need to other hard 99% (Prehensility, vision, precise 3D movement, etc.).

And if you sorted the hard 99%, what's the point in specialising in cutting onions, when the same exact skills are needed to fold and put away laundry?