Welcome to the SmartThings Community, @Sangmin_Kim!
The device integrations shown in “My testing devices” are those with a “Development” status, which means that only the developer and other members of the same organization can see them.
The devices that appear in other sections of the “By type” tab, for example, “Thermostat” are the integrations that were certified and published.
It will depend on the configuration of each ST Schema project because the one in “My testing devices” could be using a different URI.
Can you provide more details about your use case, please? Are you seeing unexpected behavior?