I thought someone would say that :), that's a combinatorial optimization that happens to work in the exact scenario I described, and assuming no further constraints.

But you lose out if you instead want to do 2 years on 2 years off, or if your one-year employer doesn't want you to work July to June, or if your year-off plans don't work July to June, or any number of more complicated scenarios. My point stands that the system isn't designed to support this kind of irregular high-income work.