No, they’re claiming that an account played for 21.5+ hours per day, for months on end, is likely to be account sharing and/or botting and should be investigated to confirm if this is the case.
If you were walking towards the front door of your house and you saw smoke pouring out of the roof and windows wouldn’t you check to see if your house was on fire? You don’t know for certain it’s on fire, but it sure would look that way.
Whereas I’m perfectly happy to state that I think it’s way more probable that multiple adults are account sharing and/or botting, than a parent + minor child are sharing an account for 21.5+ hours a day, for months on end. Especially when you see the number of accounts that are doing this. I just don’t believe there are that many (if any) parent/child combos doing this.