It is clear that OpenAI has adapted the language to a scenario they now have, where the model is not immediately shut off (or even shut off for many hours) simply by running your balance into the negative or even past the hard limit you set. There are several anecdotes of those with prepaid billing being at a negative balance - like hundreds of negative. No safety against abuse. And OpenAI will get their money.
That is not a problem to those with monthly billing accounts. There is no negative balance, there is only the monthly bill amount that will be charged. Click “buy credit” on a monthly account, and that is what will be used first and your outstanding balance will remain.
The concern in this topic is about those who had been transitioned from monthly billings accounts to requiring prepay. If that switch happened March 15, lets say, then the account may have accrued a $50 positive balance owing that would be billed in April. And it still would be billed in April, the purchase of prepay credits would not reduce or terminate that prior billing, it would only pay for future use.