This doesnt make sense - the 16-bit modr/m byte (required for indirect register access) doesn't use the 'regular' opcode numberings, and the 32-bit modr/m byte

This doesnt make sense - the 16-bit modr/m byte (required for indirect register access) doesn't use the 'regular' opcode numberings, and the 32-bit modr/m byte can use any GPR, so BX is not special anymore (as mentioned in the article).