I believe it is the norm. Windows that open are placed higher, for safety reasons. Then, a rail is placed in front of the window to keep adults from leaning over into the opening or easily going through the open window. It's exactly the system that is used for balconies, canyons and other high places. Handrails are there so that people can grasp them (some people experience vertigo when they see that they are up high) and so that people can have a clear boundary of where they are to stand.
This is equivalent to the people who sit their kids on guardrail tops and guard walls at Grand Canyon (or other high places). Most people wouldn't hold a toddler in their arms right at the unguarded edge of Grand Canyon, and most people do not sit their kids atop Grand Canyon guard rails, either (but some do and some allow their children to play on the guard rails and guard walls). It is so nervewracking to watch. I watched a family allow their 5 year to walk atop the low barrier (made of rocks) on Bright Angel Trail. The drop beyond was only about 100 feet, and of course, at GC, that looks like a "short" drop. It would likely be fatal.
Many of my (college) students believe that it is easy to survive a 20-30 foot fall (so they think it's fun to dive off second or third story balconies or windows into swimming pools). In fact, even a 5-6 foot fall head first onto a hard surface can be fatal and if it is not fatal, it can result in very severe injuries. We live in a culture where people post youtubes of very risky (and often painful) behaviors and it's intended to be humorous. Everything is fun, until it's not.
I do think that Anello wanted to be the "fun grandparent" and loved to pick up Chloe and hold her such that her head was at least as high as his (whereas, there's much to be said for adults lowering themselves to the toddler's level, because risk assessment takes on new meanings when we look at the world from 3 feet off the ground). Had Anello done this (knelt while Chloe explored the window area from the safety of the floor), he'd have looked up and seen that the window was open. Even the slowest or most distracted of minds would surely have seen that the lower windows don't open for a reason and that the handrail exists for a reason.
I know it's harder for bigger, older people to squat or kneel easily (but we see him do it in that picture with the dog) and it should be ingrained in any child-carer that a kid's world is meant to be explored from the POV of a kid. That's the very basic premise of childproofing (you go into a new hotel room, you look at the outlets from the POV of the baby/toddler, you look at power cords and window blind cords from the child's POV, you look at how balconies are structured and how windows open from a kid's POV. I believe it's reasonable to expect adult carers to do this.
But people on vacation, in particular, tend to abandon common sense. The child who fell at Grand Canyon was being "watched" by her parents (and had just been sternly told not to go near the edge). But she was a kid, and her reaction was to run right toward the edge. In that case, the parents should have been in physical control of their 4 year old (holding hands or using a stroller), not merely using verbal commands. My second child was such a stroller escape artist that GC was off the table and in fact, I worried when she went there as an adult (she's still distractible, but as she had her own child with her, lo and behold, she was super cautious).
