Isn’t another risk if the market tanks within the first few months, because you will have to pay the withdrawal penalty from the CD out of pocket before you have the interest accumulate? This risk seems proportionate to the benefit (given that we have more than one huge correction every 50 years, there is a > 2% chance that the market will have a huge correction in the first year).
You say that you are moderately confident that the risk did not include this case, so I’m likely missing something (or you need to do a moderate update).
It seems the whole deal is dependent on margin interest rates, so I would appreciate more discussion of the available margin interest rates available to retail investors and what rates were used in the simulations. I would also like more evidence to the statement in comments that says “the fact that a young investor with 100% equities does better *on the margin* by adding a bit of leverage is very robust” to be able to take it as a fact, as it only seems true at certain rates that don’t seem obviously available.
As one datapoint, my current broker retail margin rates are high, at 8.625% under $25k, 7.5% > $25k loans. Given that this is a period of relatively low interest rates, (and I would expect it to be higher in other periods), it would not seem like an indisputable fact to me that a young investor expect a better return by investing $1 on the margin after interest. But I have no idea how it compares to other brokers. (Unless you are considering leveraged funds, which I considered to be a different beast).