Hello,
The ICM-20602 datasheet does not give any information on what type goes into ACCEL_COM_X/Y/Z_THR. The THR register is only 8 bits, but the accel data registers are 16 bits. Is this the high byte of the threshold LSB based on whatever scale the sensor is set to? This makes the most sense to me, although it doesn't seem to work:
icm->reg_accel_wom_x = (int16_t)(x_threshold * icm->accel_divisor) >> 8;
As an aside, this datasheet has a lot of issues of both clarity and content. I see that the only revision is 1.0, which is concerning. With no companion example code, this makes developing on this product a chore.