How so? Arithmetic on FPGA usually use the minimum size that works, because any size over that will use more resources than needed.

9-bit bytes are pretty common in block RAM though, with the extra bit being used for either for ECC or user storage.

10-bit C might be close to non-existent, but I've heard that quite a few DSP are word addressed. In practice this means their "bytes" are 32 bits.

  sizeof(uint32_t) == 1