You don't seem to be saying anything different than me in terms the unlikelihood that someone would buy a whole BTC at once, and even an aggressive DCA strategy in the ballpark of $100 per week is going to take 6 years just to invest up to $31k, so it may well not even be fast enough to get 1 BTC in 10 years at that $100 per week level of DCA...
But yeah there are some people who can be more aggressive than that.. but usually not regular folks.
Sometimes $100 a week is too heavy for the regular person and even more so if they live in a country that has lower wages compared to other countries. Moreover, for those who are young and don't have a permanent job, of course they might not be too focused on investing $100 every week in Bitcoin. But time is not a problem in long-term investing because time passes so quickly and the $10 or $20 they invest regularly will not feel they can reach 1 BTC someday.
Yeah that's true because in times of investment is better accumulating with the little amount you can afford on a regular basis than investing or accumulating using a higher amount that could possibly affect the investors financial strength.
And one of the things that should also be considered in times of accumulation is being able to adjust the accumulation process if the need arise, perhaps while accumulating using a specific amount if in some time in the future you have a lot of cash flow coming from different source you could then adjust your accumulation amount more higher.