The most I've been able to get out of all you've said is entirely correct and true.
You have a tremendous viewpoint of what the DCA strategy is all about (although with some little flaws) and how beneficial it is to those/choose chose to adopt it as their method of Bitcoin accumulation.
Inasmuch as what you've said is correct, it can't always work out as expected, although it could work out most of the times, but not always, due to the unpredictability of the market, you could still split the money into smaller units and still buy through a dip or buy more when prices are high and less when prices are relatively low, which could actually be considered as loss.

It's doesn't really work all the time regardless of the fact fact that it's actually one of the most effective techniques when accumulating bitcoin because by splitting your investment into smaller units and using them to buy at different price points.
This method is very essential because it helps you not to invest too much at the wrong because you're investing in units, and it can also help to stabilize your emotion and balance it a lil bit more in the middle of a market fluctuation.

Another way that it proves it's importance is by reducing timing risks, since you're not actually investing too much amount all at once, which could actually be the peak of the market. It also averages out the cost of Bitcoin, since your overall cost per BTC will be averaged out, which is a very effective method of almost eliminating the impact of market fluctuations.
HODLing for a long time is undoubtedly another effective strategy that'll reduce the effect of the market fluctuation.