Another vote for breakaway cat collars! I just feel like you never know. Kaji for the most part is very obedient and predictable. As long as I control his environment, he thrives.
But, and it's a huge but, he panics because he's scared easily. In that split second, I lose total control and he has a tendency to just run. The collar is just a safety precaution. I know a lot of people think "what's the point? They'll just fall off." which is simply not true. They're quite sturdy, and only fall off in an emergency. Maybe the collar you posted about follows the same design.