Coyote Piper - S3-E9
Trivia: The title for this episode is a reference to the film Coyote Ugly. The film is set primarily in a bar named Coyote Ugly where the 'coyotes' dance seductively on the bar. In this episode of Charmed, Piper dances on the bar at P3. Additionally, the actress who plays the main character in Coyote Ugly is named Piper.
Answer: That was a mistake in the series.
Also, the episode is called 'Babies First Demon' and this alone tells us that it's Wyatt's first time in the field (so to speak) and as the sisters say, they've done a good job of clearing up their own magical messes so far. Nobody really knows how advanced Wyatt's powers are, or will become. That's why the cleaners appear, to nip things in the bud. The Cleaners didn't want to chance that the sisters could clean Wyatt's magic up, just incase they couldn't. Therefore intervening themselves, just in case.