Maybe not a simple typo, but with two errors it's plausible. The iPhone X's A11 CPU is supposedly slightly faster than the A10, which is 2.3 GHz. So, place a decimal between the 2 and the 4, and change the M to a G, and you have a reasonable figure.

the original benchmarks the author likely used had a screenshot of some benchmark tool's output. It showed a 24 MHz processing speed which I also thought was weird. Could just be an anomaly in the benchmark tool.

Either way the tool they used (geekbench) apparently looks into chip-specific optimizations for tests and the rest of their process is not disclosed so it's possible all of their benchmarks are non-uniform (again based on an optimization ticket here: http://support.primatelabs.com/discussions/geekbench/18305-o...)

That came from geekbench, and the geekbench folks have already said they can’t determine the MHz of an A11 yet.