I believe that this has something to do with the new WhatsApp Desktop beta for multi-device. Every time I log in with a new device, I see the "security code changed" message.
It's a bit annoying because it undermines the value of the security notification. People get used to it (the boy that cried wolf). I used to get people asking if things were ok if I moved to a new device. This won't happen anymore when people get ten of these a day