This ignores the obvious solution of not cutting all the way through. If every other radial cut is only through half the layers, you avoid making the inner pieces too small. It's funny how common it is for people to claim some sort of optimality with lots of math and analysis while completely failing to consider a better possibility. Never take seriously claims that someone found a "mathematically optimal" way of doing something. They didn't.

I’m not going to try to make consistent partial cuts down through an onion. I’m going through to the cutting board every time.

Real-world optimal is often just "whatever works best without making you cry (too much)"