Revealing mistake: While Piper is trying to convince Paige to be at P3 for speed dating, Piper says, "I will resort to whatever I have to, besides you might actually meet someone you like," and after the quick shot of Paige, when it cuts to Leo holding Chris as he's standing in the doorway asking for baby Tylenol, the mirror's glass is green at the right side of the screen - for the special effects editing of the fake reflection. (00:04:40)
Continuity mistake: After the opening credits, while Piper tries to persuade Paige to help with the speed dating at P3, in two shots facing the bed and in the shot facing the mirror showing the "Jaime and Jo Bennett" reflection, the lamp on the far side of the bed is turned on. When Leo is holding Chris he walks past the mirror, and in this reflection that lamp on the far side of the bed is turned off, but in the next shot facing the bed that lamp is on again. (00:04:55)
Continuity mistake: After Antosis and the Imp Master are vanquished, in a following shot we see Phoebe wearing a robe and sitting on the bed, then we see her "Julie Bennett" reflection in the mirror, but notice that even though the style of the robe is the same, the colorful designs are quite different in the reflection. This happens again later when the sisters and Leo are seen in the mirror's reflection, as they undo the spell to reveal their true selves. (00:33:25)
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.