You already write why that is mathematically impossible, so the logical conclusion would be that it is not meant to be interpreted like that no? Language is not maths, no risk doesn't mean the risk is zero. It means the risk is unlikely.

These are complicated topics. The people buying crypto at Coinbase are not sophisticated investors.

It is entirely reasonable to believe that a large proportion of Coinbase users would read, "We have no risk of bankruptcy" and choose to leave their money at Coinbase believing that the CEO must have used some financial mechanism to 100% prevent bankruptcy.

Words have meaning, and when you say, "no risk of bankruptcy" there are a lot of people that will be duped into believing that literally.

It would be a bit weird to stop reading mid-Tweet though. After the comma he says Coinbase added a new risk factor to the list as required by the SEC.