Open an IUL illustration and the crediting column shows one number, repeated, year after year. Say 6.5%. No index has ever delivered 6.5% forty years in a row, and the illustration isn't claiming it will. It's showing you an average. The problem is that averages and actual account growth aren't the same thing.
Here's the arithmetic. Two years at a straight 7% turns $100 into $114.49. Now take a year at 14% and a year at 0%, which averages to the same 7%. That's $114.00. Close, but lower, and the gap widens as the swings get wider and the years pile up. Sequence costs you something even when the average matches exactly. That's true of any account that compounds, and it's why a straight-line projection always reads a little optimistic.
The zero floor changes the shape of this in both directions. In a bad index year you're credited zero instead of a loss, which is real protection and the main reason people buy these. But zero credited doesn't mean zero cost. The cost of insurance and the policy charges still come out that year, so the account value can go down in a year the index goes down, even with a floor at zero. Two or three of those early on, and the illustration you were shown stops describing your policy. How the floor and reset actually behave is at the annual reset and the zero floor.
Regulators have tightened what carriers can show. AG 49 and its successors cap the illustrated rate and limit how much a bonus or multiplier can add to the picture, which is why illustrated rates today look lower than the ones people were handed in 2014. That's a good change and it still doesn't turn a projection into a promise. The levers the carrier can move afterward are at cap, participation rate, and spread.
So read three things instead of the headline rate. Read the guaranteed column, which is the floor the contract actually obligates the carrier to. Ask for the illustration run two or three percentage points lower and see whether the plan still works. And check the charge structure, because a policy that survives a lower rate is a policy that was designed with room in it.