This question already has an answer here:
Prompted by this question: Who is "He that flies" in Lord of the Rings?
The simple answer from comments
"He who flies" is a way of describing someone who is fleeing a battle. It doesn't refer to a particular character.
This question would be better on the English Language Learners Stackexchange, since it’s purely about the meaning of an English sentence, not any SF or fantasy content.
while some have made the case it should remain
But [the OP] didn't know that at the time he posted the question. For all he knew, the phrase might refer to some "magically empowered aerial reconnaissance asset" rather than just a figure of speech regarding cowards and their exaggerations.
Should we leave it alone as-is, or close it as being about an arcane English phrase?