Magic strings create an implicit dependency between components. Implicit dependencies can make understanding how a system interoperates and the relationship between components more difficult. Where does this action come from and who else cares about this? These two "save" actions have the same name, but are they actually the same? Magic strings used like this are kind of like globals.
Rather than using magic strings, exporting and consuming a constant from outside the file it's defined in requires creating an explicit and directional relationship between the definition & the consumer: `import { CONSTANT } from './place'`.
The boilerplate is undesirable but I think showing explicit, directional relationships between files via require/import is more valuable for the overall cohesiveness of the system than the few lines of code you save.
I agree with the article that when constants are defined and consumed in the one file, constants are perhaps overkill, though maybe there's benefit to maintaining the same pattern for both internally and externally consumed constants.
Also agree with the overall sentiment of the article, should definitely be questioning and evaluating the cost benefit of best practices for our specific use-cases rather than blindly cargo-culting the dogma.
How? React Native is for cross-platform mobile applications while Rax only works in a web browser, as far as I can tell.
edit: Appears you're right, from the Rax tutorial [1]: "Rax is like React + React Native, you can use a component in the same way both in native and web as building blocks. " I guess this is possible because it's built on weex [2].
1: https://github.com/alibaba/rax/blob/master/docs/tutorial.md
2: https://weex-project.io/