Earlier quoted context omitted.
While using a compiler framework written in C++, yeah.
I'm with you on the broader sentiment that Rust isn't making nearly as many inroads many people think. But this example is silly. Do we say "FORTRAN is eating R" because R uses BLAS/LAPACK/whatever via gfortran? Nah. A zillion languages use LLVM.
But this is not a good analogy. Rust is being talked about explicitly as "better C++", with a huge and vocal group of online people going around and saying that the world will end if we don't rewrite everything in Rust, or that no new C++ project should be started today with Rust being available.
Very few people, if any, put R against Fortran in this way, so the fact that Fortran libraries weren't rewritten in R doesn't contradict anyone's expectations.