The blog post is really about language design, because you definitely should not write a filter method for your custom iterable class in python; you should make it use the language’s interface’s for “being an iterable”. Language design involves APIs offered by the language, but isn’t really the purview of most people who write APIs.

If a suggestion on language design would gain something at the cost of readability, anyone should be very skeptical of that.

Those things together explain why I am evaluating the post mostly in terms of readability.