That just isnt true. If the 529 plan is invested in the exact same indexes, a 529 will almost always have more funds in it than an IUL. the IUL will miss out on all the index dividends that IUL & FIA dont receive, the IUL will have internal costs for the insurance. Most states give a tax deduction for contributions, so instead of paying an IUL load of 6% on every payment, they may actually get paid 4-10% in state tax deduction. lastly, a 529 distribution is tax free if used for college whereas an IUL is only tax deferred or tax free if you borrow from it, not merely take the money out.
So I am going to quibble with the first part of your argument regarding dividends.
Dividends are built into the stock price. A stock that has a 5% dividend and is $100 the day before it trades ex-dividend will trade at $95 the day after. If we measure the index value at any time during the year we trade with accrued dividends of some amount.
It is why dividend selling can be a FINRA violation.