Twitter's SEC filing: "In making this [mDAU] determination, we applied significant judgment, so our estimation of false or spam accounts may not accurately represent the actual number of such accounts, and the actual number of false or spam accounts could be higher than we have estimated."

Neither side said bots, but bots _should_ be a subset of "false or spam" accounts. They basically used "our judgement" and give themselves complete discretion. And 5% is a nice round number plucked from nowhere which sounds awesome! Providing proof of that to a Banker or Backer (or Elon or a future Jury) isn't therefore possible or intended. It's marketing spin in an SEC filing.