your numbers of holding 6-12 months of cash would be difficult to maintain, even for rich folk since such cash would be losing 5-10% or more per year in value.
That risk of losing your job during those times (2020, 2022) that BTC dropped 50%+ is why you have a "backup fund". You're right that there's an opportunity cost involved, but that's not the same as "cash is losing value." Your backup fund shouldn't be sitting in your checking account, it should be in a HYSA/T-bill etc, which are currently paying ~4% in interest, which is about even or possibly a tad above with 2.5-3% inflation. So, there's an opportunity cost compared to BTC returns, but cash isn't seeing a 5-10% bleed.
Perhaps prior to 2020, the dollar (and so western countries) were experiencing a debasement that was between 2% and 3% per year, or at least it seemed to have had been the case in terms of seemingly regularity of prices for goods/services.
After 2020, the rate of debasement was at least 5-10% per year and perhaps even more.
You can do what you want in terms of keeping so much cash, yet I still assert that if you are brand new to bitcoin and you are building up cash prior to building up bitcoin, you are failing/refusing to recognize/appreciate the value of bitcoin, and even guys who might have irregular cashflows (including unexpected income and/or expenses), it seems quite rare that guys should be holding 6-12 months in cash, especially if he does not have any other investments, yet perhaps in the context of a businessman, there could be some things that he owns, such as capital assets and property related to his business, so various businessmen may well have somewhat unique circumstances that tend to not be very applicable to an overwhelming majority of normal people.
By the way, even on a forum like this, we cannot presume any kind of western income and/or western opportunities for higher wages, and there are a large number of guys who struggle to maintain reasonably high levels of discretionary income so that they can invest in the first place, and so the solution for an overwhelming number of guys participating in this forum who have discretionary income would most likely relate to figuring out reasonable ways to build up both their bitcoin investment and their back up funds... and it would be close to retarded for them to be overly focused on building up back up funds at a speed that is faster and/or greater than building up their bitcoin... and the reality of the matter is that it would most likely be more prudent for them to give greater weight to building up their bitcoin as compared with their back up funds and to ongoingly be keeping themselves marketable and earning an income that gives them sufficient discretionary funds on a regular and ongoing basis.
So there may well guys who are coming brand new into bitcoin and perhaps they have only 1-2 weeks of back up funds, and they can get started building up their bitcoin from where they are at rather than building up their back up funds before getting started in bitcoin, so let's say that such beginner to bitcoin has an income of $20k per year, and expenses that are about $15k per year, so then that means that he has about $100 per week of discretionary income, and he may well get started by putting $33 per week into investing, $33 per week into his back up funds and $33 per week into discretionary consumption, so that after 1 year of investing he would have had invested $1,716 into bitcoin, put $1,716 into his back up funds and discretionarily consumed $1,716. After 10 years, he would have had built up $17,160 into each, even though he may well might not have had needed to put more than $3,750 into his back up funds, since that would be 3 months of his expenses, and sure maybe he could keep between $3,750 and $5k in back up funds, and it makes more sense to keep greater back up funds (and even to put some of that back up funds money into other assets - that have less of a priority than bitcoin) as his bitcoin investment size gets larger.
Poor people likely have more reason to make sure that they are investing into bitcoin as compared with richer people, even though bitcoin is important for all people, even though richer people might not realize the debasement of the dollar as much or even how great their lifestyle is affected by the debasement of the dollar - that includes the need to invest into something solid like bitcoin, as compared with poorer people... yet one of the problems with poorer people continues to be being able to ongoingly generate enough income to have discretionary funds that they would be able to invest into bitcoin on a regular and consistent basis, and perhaps even in an aggressive way, since if the amounts being invested into bitcoin are small, there may well be some needs for aggressiveness in regards to investing into bitcoin as compared with having the wrong kinds of focuses in terms of holding onto trashy cash that is debasing so fast that it becomes problematic to be holding it, unless the holding of the cash is offset by the holding of a good (and pristine) asset such as bitcoin.