I agree that a person should not be dipping into his emergency funds for BTC buys, but there could be situations in which it makes sense if there is variability in income and expenses, and there is also a decent sized emergency fund. There also may be decisions to buy a certain quantity of BTC no matter what, so if the cashflow over several months is fluctuating, the income might not meet expenses, and yet there still might be expectations that the following months or the month after, the emergency fund will be able to be diminished with the short-fall, and part of the reason to have an extra large sized emergency fund is to be able to buy BTC every month/week. . or whatever might be the priority that is pre-established.
Anybody that uses funds for emergencies to invest in Bitcoin is not a wise investor because problems can come at anytime when he/she will need some money that he will use to settle down some things that needs to be settled..
Having an emergency funds might make an investor to hold more longer than he or she planned to hold. Reasons are because when you are saving and still accumulating Bitcoin and on the other hand you have funds for emergencies, then what will the person want to sell his coins for? Nothing,,, unless they will want to use some of the profits to complete a project and other things that can be bring more money to them during the week or month.
There are some people who works in a company that don't pay workers salaries on time (delays payments) and those people if they are invest in Bitcoin and they are not saving some funds for emergencies and just saving for nothing, by the time month end and there is no payment they will want to sell some coins and use the money to support them self untill payment is made.
Even though you are correct that if an emergency fund is not very robust, then a person probably should never use the fund for anything other than emergencies.
However, I doubt that there is any strict rule in regards to whether someone might choose to use his emergency funds - so maybe if I exaggerate the hypothetical a bit more, you might be able to understand how an emergency fund might be used in a floating kind of way.
Let's say for example, a person starts investing into bitcoin, and at the same time he is building up his emergency fund, and so his regular salary ranges between $300 and $1,200, and most of the time, his salary is more $700. His expenses are right around $500, and let's say that he has 2 months of expenses saved up in his emergency fund saved up ($1k), but he wants to get his emergency fund up to between 3 and 6 months ($1,500 to $3k)... and so maybe he will not really be comfortable buying bitcoin until he get's his emergency fund up to 3 months, but he does not want to forgo investing into bitcoin, so he decides that he is going to buy $50 worth of bitcoin no matter what, so long as his income for the month is greater than $550, which is $50 greater than his expenses, and if the income for the month comes in greater than $550, then he will split the extra between his emergency fund and buying bitcoin, so if he ends up earning $1k for the month, then he has made $500 extra, so he could put $250 into bitcoin and $250 into his emergency fund.
Maybe he also decides while his emergency fund is between 3 months and 6 months, he is going to buy $100 worth of bitcoin no matter what, and so there could be some cases in which, and sure there could be cases in which he has to dip within his emergency fund to accomplish that, especially if his income were less than $500 for the month.
So then maybe once he gets his emergency fund up to 6 months, he might decide to buy $500 in bitcoin each month no matter what, and there also could be cases that he ends up dipping into his emergency fund.
Let's say that he continues to invest and build his emergency fund, and his emergency fund has gotten up to 9 months worth of expenses (which would be $4,500), so at that point, he might decide to buy $1k worth of bitcoin every month no matter what until his emergency fund goes back to 6 months, and then if his emergency fund goes back down to only 6 months, he will modify his approach to be more conservative at that time.
I am merely giving this as an example to show that there could be cases in which an emergency fund ends up being greater than it needs to be, so then there could be choices to dip into that emergency fund, based on the size of the emergency fund being greater and perhaps having a greater ability to float non-emergency type issues. .and so what you call it might be an argument about semantics rather than recognizing that there can be ways in which some portions of the emergency fund might be treated more strictly than other portions, especially if such emergency fund gets built up to be fairly robust in size relative to expenses (or expected expenses or even how much extra might be needed to keep in the emergency fund for unexpected happenings, which the punchline, like you said Su-asa is not to get to any kind of point in which you run out of emergency funds and have to dip into your BTC investment at a time that is anything other than your own choosing. .which depletion of your emergency fund would not be a good place to be... in part because it seems to be largely preventable.
If one can save bigger amount for emergencies in 9 months, he should just concentrate on the investment for some times until the emergency funds is low then he can continue saving for emergencies, like after removing the monthly expenses from the monthly salaries hes receiving then he should just put the rest of them into Bitcoin.