One of the golden rules of babywearing safety is to keep your child's face in sight at all times so you know their nose and mouth are clear of anything which may interfere with their breathing.
With a toddler or a preschooler, when you use the hood with both sides clipped, their heads are big enough to fill the space under the hood enough so that the fabric of the hood doesn't pull in around the side.
With a younger baby, this is not the case. So not only can you not see your child, but the hood fabric can often pull in front of their face, putting their airways at risk.
The solution for this?
If you are using the hood for sun protection, use a hat instead.
If you are using the hood for extra support while your child is sleeping, then bring the hood diagonally across your child's head to the opposite side before you fasten it in place.
As you can see by the second image, it is much easier to keep baby in sight using this technique.