That is very strange. According to the manual, in a list of 18 safety points, the 3rd point warns not to immerse past the halfway mark and to reduce the water amount if splashing is above the midpoint. Perhaps Jeff will pop in here again and clarify things. I thought it sounded strange too so I'm hoping he pops in but maybe it is just to ensure you don't accidentally allow it to get too high, because if it does start overflowing the water could get to the colored part which could then affect the electronics, etc.? I have never held one in person so I'm just going off of pictures I've seen.