Only someone who is under pressure could buy high and sell low, and of course an impatient trader could as well sell off due to lack of knowledge to understand how cryptocurrency works. But of a true if they understand that cryptocurrency is circular (halving) in every 4 years circle they would understand not to sell low and buy higher. On a Norm when the market is low that is when they should have accumulated more of the coins than just dumping.
Majority of the newbies won't understand this clear point that you made regarding buying low and selling high approach in Bitcoin investment, most of the Bitcoin traders who engaged in this approach of buying low with the intentions of selling off high to make profits still end up selling lower than their bought when if the market moves opposites their direction of expectations, this have become the major yastic for their continued losses, and the reason why many of them complain about this approach of buying low and selling high, and the major reason why they act that way is because of they lack of knowledge and patient to wait for the market to recover back before selling they Bitcoin holdings.
Another factor that drive those buying low and selling high into loses is using of high leverage when trading on the future market, it is very important that no matter how low your Bitcoin entrance price is, if you use a high leverage let say 8x,- 10x leverage toh risk losing your investment if the market make a sharp correction downward.
So for best results, apply this approach on spot trading by buying Bitcoin and storing it in your wallet, looking away from the Bitcoin for as long as you can and have a sell price benchmark in mind, never get tempted to sell off your Bitcoin when you are at lose unless when you are trading leverage which is a gamble like Bitcoin approach.