If that was the only other choice, then it's true it would ruin the pacing of the fight and it would be even worse than using the second half of the episode to flashback the first half. But possibly there could have been other ways, such as Wing explaining it to Gon and Killua when they start their formal training under him. Then it would have been a literal lecture in every sense of the word, and nobody could blame the show for making it look like a lecture to the audience as well.