I don't think your code example supports the point you're trying to make. Of 3 lines of non-logging code, one of them is AWS-specific, and so would need to be refactored to use another FaaS platform. That's what lock-in refers to. It's not saying you cannot migrate at all, it's just saying that there's a refactoring cost to swap out the platform APIs.
If you can get the same message-delivery semantics from Google's message bus, then the refactor would end there, but if you happen to be depending on a feature that's not implemented on your new platform, then you might have to refactor your application logic further.
Furthermore, you still have to get your code into production, upgrade it, monitor it, and ensure that the other functions that it, and all of that currently tends to depend on platform-specific tooling.
Much of this is also the case in the VM-based PaaS world. But, there you have projects like libcloud that can abstract some of the differences away. That feature gap is pointed out in the OP article, which makes it clear that the lock-in issue isn't a fundamental defect with the functional paradigm, just a side-effect of the FaaS offerings being young.