Your card holds more than most groups need. So each group carries its own version of it.
Decided once, when the group is made
When a group is created, the organiser chooses what it shares: medical details, insurance, emergency contacts, documents, driving licence. That choice is fixed from then on, and everyone sees it before they join.
It cannot be widened later. A group you joined for a weekend cannot quietly start asking for your medical history in March.
What every group sees
Your name, your photo if you added one, and the phone number on your card. That is what makes a member list useful at all.
What only some groups see
- Medical: blood type, allergies, conditions, medication, and pregnancy status if that group was set up to include it.
- Insurance: EHIC, travel and national policies.
- Emergency contacts and next of kin.
- Documents: passport and identity card, including any scans.
- Vehicle: driving licence and car insurance.
Leaving
Leave a group and your card is removed from the other members' phones the next time they connect. What somebody exported or photographed before that is outside anyone's control, which is the same as with a piece of paper.
The rule of thumb: join groups of people you would hand your phone to, and make a separate group for the trip where you would not.