Yeah, but nobody says you'd need to use the full 60Hz. When sample twice, three or four times to reduce the noise by averaging, you'd still come out with more than 9Hz.
Besides, you could implement a moving average filter even with 60Hz and trade in noise for motion blur.
Anyway, Mike seems to assume that the complete signal/image processing is done in the FPGA/ASIC, so this would make it much harder if not impossible to change the 9Hz anyway.