You can be briefly distracted when you drop your keys.
You can be abruptly distracted by a sudden noise.
You can be partially distracted if your mind briefly wanders to a conversation you had last week.
It doesn't have to be a twin sister who needs attention.
And at any point during this your well-trained, docile, non-bolter can suddenly do something unexpected. Like bolt. Or just go a different way a short distance. Or anything. And then, tragedy.
Toddlers are unpredictable. It's not about twins, singletons, sex. The poster was asking about age. People are giving their examples, based on their children's maturity levels and ages. And helping the poster consider age in context. All very relevant.
You got lucky. Children are unpredictable. Having read such a terrible thing to have happened, I can't believe you're doubling down on this.
Because also - since you're talking about relevance - your thoughts as a non-user were never even asked for...