I think maybe this post would make more sense if you were familiar to its antecedent [0] which compares existing closure extensions to C. IIRC the comparison was in the context of considering designs for standardization.

[0]: https://thephd.dev/the-cost-of-a-closure-in-c-c2y

C does not currently have closures, the post it looking at their performance properties with an eye for what form closures should be added to the standard.

The post is about a potential new feature of C. The author is working on the C committee and has contributed new C features in the past.

Completely missed the point of the article, this is about ongoing C2y efforts at WG14.