Chick Flick - S2-E18
Character mistake: After the horror movie characters were killed in the attic, the sisters hear the door bell ringing. When they get to the bottom of the stairs and start walking towards the front door, you can see the actor playing Billy smiling even though they're all supposed to be on edge.
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.