shouldn’t it be converted
Not if you follow my instructions. The compiler stores the 16 bit value produced by the following line in the correct byte order.
int16_t acc_x_value = (acc_x_high_byte<<8) | acc_x_low_byte;
The DEFINITIONS of “high byte” and “low byte” eliminate any possible confusion.
Named bytes have no “endianness” and it does not matter where or in what order they are in memory. High and low bytes need not even be consecutive.