from your explanation it means the rule is self contradicting and should be looked into for a rephrase. Because if its not illegal to own multiple accounts then banning all multiple accounts linked to a faulty user should be put in view. The rule can be rephrased to say one account to one user and owning multiple accounts at owners risk. Otherwise this rule is just self contradicting and should be open for review.
Creating multiple accounts is not illegal, and having multiple accounts does not increase or decrease your chances of being banned. The main and alternative accounts are one unit of you personally, and the object of the forum rules is you, not each account.