Those whose portfolio is already in a decent size might not care about DCAing when the price of bitcoin is pumping because they will only be able to buy very little quantity due to high price and that might not have any effective value on their portfolio. So such investors only prepare to buy bitcoin at the dip in order to buy large quantities at a cheaper price.
There is a different between having a decent size amount of Bitcoin and having a Sufficient amount of Bitcoin, so actually no matter how decent amount of Bitcoin an investor would have or the price of Bitcoin getting higher it will never prevent them from there continuial investment because they have not gotten to the point that they would saiy they have a sufficient amount of Bitcoin on there portfolio.
I believe that part of the problem that comes when someone builds a decent amount of bitcoin, and then if the BTC price appreciates in value, then the person may well feel that his ongoing contribution is hardly making any difference, and surely there may be quite a bit of truth to that, which can cause some disincentives to continue to buy and to just let the investment into bitcoin ride out and maybe invest into other things, so at that point they are starting to reach a potentially reasonable conclusion that they have accumulated enough bitcoin - while still not being at fuck you status or even having any ways in which they might feel safe from having so much invested in one basket.
Another part of the problem, might come in which the person is valuating the BTC that he holds based on spot price which surely fluctuates a lot and then he might decide to cash out some bitcoin for consumption purposes rather than diversification of investment purposes, so in that regard, it could still be o.k. to take some profits, as long as he does not end up overdoing it and as long as he mostly attempts to be reasonable and prudent about it, and maybe even replacing some of his investment later down the road, so there can be dangers and delays in getting to fuck you status and even temptations that cause the BTC accumulator to stop accumulating and maybe even ending up interfering (or sabotaging) his own abilities to even be able to reach fuck you status.
On the list, learning is very much important other than having the experience, at some disadvantageous situation one should prefer not experiencing something but instead learn from other people experience. Same way I would advise anyone entering into Bitcoin to first ascertain the basic knowledge that will enable him to maximize and secure his investment instead of ignorantly investing funds into Bitcoin and lose funds due to lack of certain knowledge.
The advice you say sounds quite reasonable because every new person who wants to become a Bitcoin investor must be based on knowledge so that at least they can know how to store Bitcoin in their own personal wallet very well. Because everyone will definitely be blind and can even fall in the wrong direction if they are not guided by the basic knowledge that must be in their own heads. And from this I think it would not be wrong for anyone to follow people who have been successful through Bitcoin and also people who have had enough experience through Bitcoin investment because this is also part of making ourselves successful in a particular field.
I would be careful in presuming that anyone starting in bitcoin needs to actually hold his own bitcoin in the beginning. Sure holding bitcoin is important and learning that holding bitcoin is what distinguishes it from other assets, but at the same time, I think that I a person (a beginner) can work up to holding his own keys and he might spend his first one or two years in bitcoin just building up price exposure and maybe learning about how to hold his own keys, and so people can be in different places in terms of how much they are able to learn at one time and how long it might take them to get to a point of being able to hold their own keys.. so I don't see anything wrong with beginners starting out with mere price exposure and realizing that they are not really owning bitcoin even though they are starting out by investing in price exposure and perhaps otherwise getting their finances and psychology in order so that they can continue to learn about bitcoin while investing into it (in a price exposure way)..
Yes, the more empowering aspect of bitcoin comes from having it (at least a decent amount of your BTC holdings) in your own possession, yet there are a lot of folks who have BTC in their possession, but also keeps some on exchanges and through third-parties too.. and so it is up to each person regarding the proportions of such and to realize the power of holding decent amount of BTC yourself... because none of us really can know when third parties, governments or even hackers might end up gaining access to coins that we are not holding in our own possession.. and yeah, hackers are getting more sophisticated too.. so anyone holding their own coins have to be careful not to get socially engineered or otherwise tricked or forced out of their coins.. which is also an ever changing topic and even very smart folks, long time bitcoiners might not realize some of their own self-custody vulnerabilities, even though it remains preferable to have a decent amount of self-custody when it comes to BTC.. but not necessarily telling everyone that you know.