I'm not sure if you're being facetious, but this is a classic straw man fallacy[0]: you've constructed a nonsensical motivation for the authors' use of Rust, then argued against that motivation.
There is superficial similarity between (1) "the authors wrote the fuzzer in Rust" and (2) "the authors wrote the fuzzer in Rust because it translates to better-quality bug findings", but the paper's authors did not claim (2), nor would any reasonable person claim (2).
More likely is that Rust is a useful language for authoring fuzzers because it is fast and supports modern abstractions while eliminating multiple troublesome categories of bugs. Fast performance, zero-cost abstractions, automatic memory management, and concurrency safety are useful language properties regardless of their relevance to security bugs.