One thing that is so advantageous to retrospectively analyzing DCA is that we can plug in some numbers to see how they play out during such time and get a bit of an automated and standard output.
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I have one thing going on in my mind for quite long i.e. DCA is also a form of lump sum investment. Like if a person is investing 10$ per week then he is like investing a lump sum of 10$ in week one and then a lump sum 10$ in week two and so on. DCA is also a kind of accumulation of Lump Sum investment that are made over a period of time. It's my own interpretation, it may or may not be correct.
You also have a valid point that anyone who invested a huge money several years ago and is ignorant about Bitcoin that he didn't invest at later stage, such are just hypothetical assumptions. The person who is investing a lump sum money into bitcoin is well aware about Bitcoin and will continue to invest in Bitcoin over a period of time.