There is some question as to whether the concentrated phenols from essential oils can accumulate in a rabbit's lungs over time. So while it is safe for a rabbit to eat the lavender plant, there are some who have reservations about allowing them to inhale the strong scent of lavender (or any) oils (including diffusers and candles).
In the video, he's adding several drops to a mix of white vinegar and water. I wouldn't think it would be a big deal to add some lavender but perhaps those with reservations are correct. In any case, as @Mariam+Theo said, the vinegar and water mix works just fine by itself.