Wow. People really are judgemental -and so many perfect parents on here! It is a little daunting.
Soooo, here is a post from an imperfect parent. I have propped and probably would again. I would prefer -most times- to be able to hold and cuddle the baby to feed but there are a few times when that is not possible. I had a FD who came to me at 4 months who DID NOT LIKE TO CUDDLE. I had her until she was about 2.5 y.o. and she never was a cuddler. She would give a hug and kiss and be off but didn't like to linger
She would not take the bottle from me with me cuddling her. I had to lie her down next to me and hold the bottle for her when she fed. I also, at that time, car pooled for one of my sons, three days a week and we would be in the car for over 2 hours each time. I propped for her then. ANYTHING to keep her content, quiet and happy for that yucky 2+ hours! If she was hungry when we had the other kids in the car one of them would hold her bottle for her, otherwise I propped it for her and she was fine.
You just never know why another parent is doing something and as long as it is not endangering the child (yes, a choking hazard is a reality but if the parent is sitting next to the child I would think that the hazard is not really a danger) maybe it is best not to judge too harshly.
Just my .02.