This is the first thing I have read that "the child had been warned not to ride the scooter the prior day" and that "Rebecca knew this."
Please provide a link, or explanation as to how you know this to be true.
Everything else I've read says he was allowed to ride the scooter in the house upstairs, that others clearly knew he was doing this, and that BOTH Jonah's home and Dina's home had "outside toys" such as soccer balls, etc, scattered throughout to accomodate his play. I remember Dina herself said as much in an interview. All of that indicates to me that both of his parents approved of "outside play" indoors, and allowed Max to play freely inside with these toys designed for outdoor use.
If what you say is true, why didn't Jonah take the scooter away from him the day before, and put it in the garage? It appears by all indications he was allowed to keep it inside. And who purchased the scooter for Max? Did he get it for his birthday just a couple weeks prior to his fall?
And even if it was true, I strongly disagree with your "reckless' statement about Rebecca. Max was a "normal" child by all accounts. Normal children do not need "eyes on" supervision 100% of the time in their own home. Or did Max have a developmental or behavioral issue that has been kept quiet, that you have knowledge of, that would have required 100% eyes on supervision at all times to ensure his safety?