Why code works with react-app preset?

[bondom]

There is used next code to enable import and jsx:
require('babel-register')({ ignore: /\/(build|node_modules)\//, presets: ['env','react-app'] })

But at the same time next code also works(react-app was changed to react):
require('babel-register')({ ignore: /\/(build|node_modules)\//, presets: ['env','react'] })

As I understand there is used babel-preset-react. But I can’t understand why it works with react-app..

Please explain this moment..