I worry about that a little, too, but sometimes I think not having to explain in those moments that I REALLY feel the need to explain would be a big relief, and like @krystle mentioned, help me to focus on my son, not the other people in the room.
You're absolutely right when you said:
Even if you had the bracelet the only ones that would truly understand would be the ones who have been around it personally and they would be the ones at your side trying to help or at the very least would know what was going on with or without a bracelet.
There's a saying in the Autism community that goes: "If you've ever met one person with Autism, you've met one person with Autism." Meaning, every person with Autism struggles differently than the next. I think that's the biggest aspect people don't understand about the condition.
THAT needs to be a shirt. I would wear it.