Showing up for reservation with less than number reserved

What happens if you make a dinning reservation for 6 people and you show up with 5 because of an illness?

There’s no penalty, just let them know when you check in. As long as at least 1 person shows up you’re fine.

I have found the ADR process and rules to be fully off putting. I am a planner - but I find the whole thing chips away at the magic.