"I expected to pay “straight” income tax on a total of $116.01."
That's correct: $100 taxable distribution from the 401(k), $16 short-term capital gain and $0.01 nonqualified dividend.
Because these are noncovered shares, make sure that you indicate that the cost basis shown on the Form 1099-B is wrong and that the actual cost basis is $100. The resulting taxable gain will be $16.
