I'm confused what you mean by the query of adding 55 + 66. I asked 5.6 Sol on Medium (but pretty sure any model would work at any level) this query:

"Can you add 55 to 66 and explain how you reached that output result"

And received this answer:

"55 + 66 = 121.

Add the tens: 50 + 60 = 110. Add the ones: 5 + 6 = 11. Combine them: 110 + 11 = 121."

Do you mean something else? Do humans do something better than this?

In my opinion this is goal post moving. Humans do many things that we cannot fully explain either without post decision rationalization, and not all intelligent humans are deeply introspective.