Stated another way, the author believes (probably rightly so) that stocks outperform cash equivalents, and they're pointing out that the "intuition" behind DCA

Stated another way, the author believes (probably rightly so) that stocks outperform cash equivalents, and they're pointing out that the "intuition" behind DCA doesn't actually add up when you tally all the contributions. DCA is just a way to choose your security/cash split at different points in time though. Their relative performance at different points in time greatly impacts the results. Any time you have additional (probabilistic) information to bear on the problem, DCA can start to look a lot more attractive. For example, if you expect that in some time horizon there will be a dip of unknown magnitude and unknown bottom timing, then DCA outperforms many alternatives including buying up-front. Anywho, just take care to blend what you know about the market (probably approximately nothing) with what your goals are (0% chance of hitting $0 vs a low chance of hitting $10M+ vs highest average yield no matter what vs highest yield predicated on being able to afford an upcoming purchase vs whatever else floats your boat). The right strategy for somebody else is not necessarily the right strategy for you.