Continuity mistake: When Phoebe and Cupid visit the memory of Phoebe revealing she is a witch to Dex, past-Phoebe has her hands down by her sides, but then her left hand suddenly jumps to her purse strap. Not only that, but in the original episode ("Rewitched"), Phoebe's hand remained on her purse strap the entire time. (00:11:05)
Continuity mistake: Episode 8x17, "Generation Hex": When Phoebe hands Paige her wedding gift, the way Paige holds it changes between shots. (00:01:20)
Continuity mistake: When Candor interrupts the Noxon demons torturing a student at Magic School, Rondok turns around to look at him. In the following shot, he's facing the other way and turns around again. (00:06:10)
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.