If they sell when certain price fall happen even if this is low percentage I guess they are not well experience trader and they just trade its because they think its easy for them to gain profit. Maybe they should not buy bitcoin at that state since they could lose their money especially if they can't relax their selves on some movements happening in the market since everything there is normal.
I assume traders can be allowed to sell even after topping little profits, that's the essence of trading. A trader is always a short term holder but we consider the Bitcoin investors to emulate a longer term holding of their Bitcoin.
Whatever that is shared in this place by anyone is mainly for educational purposes and references. It shouldn't be relied on or be taken as a financial advice. When to buy or sell your Bitcoin is strictly your call and yours alone. It is always advisable to DYOR before making any investment decision. This is very important so that if your investment goes either ways you will know it was your call and not have to blame someone else.
Seems you are taking the content from the wrong direction, I never ultimately proposed the use of the tool, it is your decision on when you decide to sell, I don't think I deemed it compulsory but it's usage can also help significantly on the appropriate time to buy and sell. So all you need do is consider it your choice, either way can still make profits from your investment.