So, this is what your disclosure says and you want to know what it means? The language is intended to give you the right to close the account, not spell out the details on how you would do so. It contains enough weasel words to allow you to implement it according to the circumstances which might include among other things:
* Consumer vs. business account
* Volume and types of items deposited
* Account overdrawn vs. positive balance
* Reason for closure; e.g. kiting vs. suspicious activity vs. repeated NSF items
Some of the perceived risks to your bank are 1) the customer will authorize a payment that was properly payable from the account unaware that you have unilaterally closed it or 2) checks deposited to the account will be returned unpaid and you have nothing to charge them against and 3) the customer is involved in illegal activity and you are facilitating it.