If you want to read a bit of Rust community criticism into the Article, I think it would not be too far off to read this as “There are lots of people claiming writing things in Rust provides better software due to memory safety, but in practice users did not care and were perfectly content with the C implementation” (presumably because the latter has no noticeable bugs).

I also interpreted the article a bit that “users” here refers to developers that make use of libcurl, that would overall like to ensure that the application that they are writing does not segfault or similar. It seems plausible to assume that some of the Rust goodwill would translate to developers that may also try to migrate their overall code to Rust to try out that backend, and potentially contribute improvements. The Linux kernel and Git for example seem to attract a lot of attention of people that want to work on migrations towards more Rust.