From what the post mentions, I'd presume the accounts were banned for promoting commercial content without an enterprise account. Most social media platforms are more concerned about non-enterprise accounts being used for promotion than they are whether or not those accounts are bots, as promotional content is the main source of income for most social media platforms. A premium but not enterprise account usually only costs a few dollars to a few tens of dollars per month, but an enterprise account can be in the thousand-plus dollar range.