That rule also applies to unsigned char and signed char. In practice I think uint8_t and int8_t are usually just typedefs for these respectively, but in principle they needn't be, so you're correct that the aliasing exemption might not apply to those.

I would tend to prefer explicitly using unsigned char or signed char rather than plain char though, partly to signal that I am treating the bytes as integers rather than character. (Actually I would still use uint8_t even though I just learnt it might not be unsigned char, because it looks clearer in my eyes, but I'm not sure I should admit it here...)