I only had one kid, and she was a handful; was diagnosed with ADHD in the 3rd grade, and it was definitely the hyperactive variety. She. Could. Not. Sit. Still. for any amount of time when she was small, unless she was engaged with something or someone. She HAD to have something to play with or an activity of some kind, or else she would be trying to get into and/or climb on anything in sight.
Any time my husband and I were out with her, we were always either trying to keep her amused, chasing after her, or both, and if she managed to get into something before we could catch up with her (little kids can move incredibly fast), we were always absolutely mortified. This was long before the days of smart phones and tablets, so we didn't even have "screen time" as an option. It was...challenging.
It absolutely blows my mind that there are parents who will capmly sit by and let their kids run completely wild, the way you described. I know they exist; I've seen this phenomenon myself, but I am baffled by it. I don't understand what could be going through that woman's mind that she would think any of that was okay.
People like her give all parents a bad name and are the topic of many rants in forums for "child free" folks.