Why would a benchmark that shows "JPEG decoding - 20000ms, Nibnib decoding - 13ms" on some microcontroller be pointless? That'd be a great benchmark, if it was provided

If the issue is memory required for decoding the author could offer a benchmark on the smallest hardware that can still do both, with memory figures provided. Or the size of the largest image that can be decoded on an RP2350 with each algorithm