You're overlooking the fact that requiring Twitter to retroactively alter its own terms of service once it provided services to the government would be a violation of the takings clause. In your hypothetical example, it's more likely that a court would enjoin the government official from use of the company with the overly restrictive ToS for official business, rather than forcing the firm to alter its policy.
I'm glad I don't live in a world where people refuse to prepare for court cases until the actual injury has happened. Many legal groups have built plans and arguments for potential injuries, either to test if their clients can do some behavior, or to have a proactive case against the government if the government takes some action. For example, many times when the ACLU challenges a law in court, they were planning for it long before the law actually passed. They can't engage in the actual challenge until there are injuries, but they sure can discuss it and plan for it.
In this particular instance, I'm not trying to launch an actual court case, so the court rules of when you have standing for a court case don't apply.