Etiquette? Seriously?

If each member of the family in question is entitled to use Pre-Check, then they are entitled to use Pre-Check.

Would it have been more helpful if they had familiarized themselves with the less stringent rules for the checkpoint applicable to Pre-Check, e.g., 3-1-1 baggie, laptop, shoes, and jacket? Yes.

Is there necessarily a linkage between their son's autism and their lack of familiarity with the process? No.

Is this seriously worth worrying about? [ INSERT COMMON SENSE ANSWER}.