I find that hard to believe. I've heard claims JIT can beat C for years, but they usually involve highly artificial microbenchmarks (like Fibonacci) and even for a high performance JITed language like Java it ends up not beating C. There's no way YJIT will.

The YJIT website itself only claims it is around twice as fast as Ruby, which means it is still slower than a flat earth snail.

The benchmarks game has YJIT and it's somewhere between PHP and Python. Very slow.