After a quick skim of the thread, it seems like yet another molehill made into a mountain.
The (required) question as to whether one has a guardian or not, means it's required to answer the question, not that it's required to have a guardian. It is common to note when a question is optional or mandatory in such a manner.
The part about bringing your guardian is under the assumption that you do in fact have / need one. If you have a guardian, bring them. If not, then don't - they're not mandating that you go out and get one.
The purpose of bringing the guardian is that, IF you do have / need a guardian, it is advisable to have them on hand, not because "meltdowns", but because since they are your guardian (if you have one), they should also be part of the interview process as support for an individual who does need support, as evidenced by the fact that they DO have a guardian.
This misunderstanding of intent is an example of exactly WHY they want people to bring a guardian, IF they have or need a guardian. So that if the autistic person doesn't understand something, or if the employer doesn't understand something, the guardian can act as a "translator", or otherwise support the individual under their care, as is their job.