That's incorrect, the verification happens fully locally. The check app occasionally has to update trusted certificates but otherwise it runs locally. No personal data is sent to any kind of server.
Do you pay cash when you go to restaurants or shopping? If you pay electronically then why do you trust the payment system? (it is not open source,reproducible and for sure your purchases contain much more data then what you imply the QR code scanner collects)
Obviously there's a risk that the person scanning the QR code does shady things with it but it's rather unlikely the app itself will. It would be caught really quickly.
