The author gave a pretty good reasoning why is it a bad idea, in the same section. However, for the demonstration purposes I think the they should have included their vision on how the request scoped data should be passed.

As I understand they propose to pass the data explicitly, like a struct with fields for all possible request-scoped data.

I personally don't like context for value passing either, as it is easy to abuse in a way that it becomes part of the API: the callee is expecting something from the caller but there is no static check that makes sure it happens. Something like passing an argument in a dictionary instead of using parameters.

However, for "optional" data whose presence is not required for the behavior of the call, it should be fine. That sort of discipline has to be enforced on the human level, unfortunately.