This is wrong. An employment tribunal can refer any contempt of court to the High Court which can impose a prison sentence. There was a case where a claimant for constructive dismissal was found to have threatened and attempted to bribe witnesses and was sentenced to one month in prison for contempt. The tribunal definitely can do something if the guidance is ignored, although I suspect revocation of access is more likely than anyone being sent to prison.
I believe the goal of the guidance is to try and ensure that any online reporting is a reasonably accurate reflection of what happens in the tribunal. As I say, I think the guidance as written is vague to the point of being unworkable. Nonetheless, the safest approach is for everyone to comply with it as best they can.