It’s best to ask for policy clarifications using https://support.twitter.com/forms/platform
This point in the terms is mostly to indicate that you shouldn’t modify the contents of tweets that users send – whether you’re adding hashtags or links or text they aren’t aware of before sending, or modifying tweets that have been sent to have the aspects when they didn’t originally.
In other words, the user should be in absolute total control of what their account will tweet at all times.
