What it means
Too early, and normal pullbacks stop out trades that would have hit target. Test when to do it.
In practice
Moving the stop to the entry price removes the risk from a trade that has started to work. Traders usually do it after a clear event, such as price reaching the first target or breaking a new swing point, so the decision follows a rule.
It protects the account and it also frees attention: a trade that can no longer lose is easier to leave alone.
What to watch for
A breakeven exit is not free. With spread and commission it is a small loss, and each trade stopped at entry that then reaches the target is a lost winner. Compare results with and without the rule on your own trades.