No: some buses let you write different sized words to the memory controller or RAM chip. For example, picture a bus that's 32 bits wide, but there are control lines that let you specify that you're writing (or reading) 1 byte, 2 bytes, or 4 bytes. During a single byte wide bus cycle you are not sending 4 bytes to the part, even though there are 32 bits connecting to it.
Certainly not everything out there is byte addressable, but neither can one say unequivocally that all RAMs have large atomic word sizes.
Certainly not everything out there is byte addressable, but neither can one say unequivocally that all RAMs have large atomic word sizes.