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When coming into Bitcoin investment there are somethings that are always confusing and it was to me too but I no better now which are.
1. How can I buy something that one of it is $60k plus and you are saying I should accumulate enough of it.
This was one thing that got me thinking but I was told that Bitcoin is divided into smaller unit and one can buy any amount of Bitcoin one wants just as your money can carry and that I can buy little by little till I get 1 BTC or even more so after that explanation I understood.
So I think some newbies also think the same way and that is why they don't believe in DCA strategy and some even lost interest because of this and that is why is good to ask questions when you don't understand something it helps you to grow.
2. The believe that one won't accumulate enough using DCA strategy.
A lot of people feels DCA strategy is a waste of time and one can't accumulate anything reasonable, I know a lot of people who has used this DCA strategy and has accumulated enough Bitcoin it only takes some years, for me the reason why people see DCA strategy as a waste of time is because they see Bitcoin as there only source of income which is very wrong, when you have a good source of income Bitcoin investment becomes more better for you and you won't have to panic of anything and before you know it you have accumulated enough.
If you don't have a source of income all your mind will be in your Bitcoin investment thinking about how it will increasing in price and since that is what is in your mind you will get tired of holding easily but with a source of income you won't be bothered and you won't get tired of holding.
Of course you raise reasonable points about unit bias and so sometimes it might be helpful to let people know about accumulating satoshis rather than accumulating bitcoin, so they could maybe buy 10,000 or even 100,0000 satoshis at a time, and then after getting up to 100 million satoshis, they will have a whole bitcoin.
Your second point about having some kind of disposable income remains important. Sure there can be periods in which folks could have cashflow problems and they could still accumulate bitcoin, but there is a bit of a problem if the person runs out of money to buy bitcoin, so there is some kind of a need to not only get some cashflow coming, but the cashflow has to be greater than expenses, especially if a person is using the money on bitcoin with a presumption of holding it for 4-10 years or longer, so the person should not be using money that he is going to need in the next 4-10 years or longer.
Going into bitcoin and putting the money into bitcoin, there is a need to understand that the money that is going in is going to be locked for 4-10 years or longer. Sure the person has the power and discretion to unlock their bitcoin invested money at any time that they want, but they should go into bitcoin with the understanding that they are not going to be unlocking their bitcoin for a long time (4-10 years or longer), and that they have to have and to maintain finances that are strong enough so that they are not going to need to or want to tap into their bitcoin investment until well into the future when they have transitioned into such stage of tapping into their bitcoin investment... which is also up to them to figure out some kind of ballpark idea about what those conditions might be, but they do not need to establish their conditions in the beginning of their investment (except maybe in sort of ballpark ways), they can figure out their tapping out conditions later on down the road.