I totally agree to all what you said here, while the DCA accumulating strategy remains the best accumulating strategy, that doesn't make the lumps sum strategy bad, the most important thing is investing when the funds is available, and sticking to your investment without you tempering with it in the future.
Then as for the case of volatility, that's just one of the characteristics of Bitcoin, and we that are investors shouldn't be bothered about that, it's only traders that should be worried, we should not forget that we are all long term holder, so why would we be worried about short term volatility? That's the cup of tea for traders, not investors like us.
DCA method is not only for long-term investment but also helps in accumulating more Bitcoins, it is a suitable method for long-term holding in all aspects, which is why DCA method plays the biggest role behind the holding of every investor. When you start holding Bitcoin and if it is every week or month then you will be busy raising money and will also get rid of extra expenses. For example, citizens of every country may keep money in their domestic bank but they get low interest, but Bitcoin is such a coin where if you deposit Bitcoin, you will be ready to get your maximum profit within a few days.
You should note that the history of Bitcoin price is right. Those who have invested in Bitcoin and have held their Bitcoin till now are present to get the maximum benefit of their Bitcoin. For this reason I say Bitcoin is the only trusted coin in which all people can be successful by investing in it in a long-term manner.