A matched-load-has-no-reflected-step scan sets the load impedance equal to the line impedance, checking that the reflection numerator Z_load - Z_line goes to zero so the reflected step V_- vanishes row by row. The arithmetic is exact only for the stated load impedances, line impedances, reflection coefficients, reflected voltages, and rows in the ideal uniform-line, matched-load model. Real lines add loss, dispersion, connector mismatch, source impedance, finite rise time, probe/calibration limits, finite precision, and measurement uncertainty.
A matched load has reflection coefficient zero. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
A matched load has the same impedance as the line
The line and load are both 4 ohms, so the reflection numerator is zero.
Zload−Zline=4−4=0
Zero coefficient means no reflected step
The reflected voltage is 0 volts, so the echo from this boundary is erased.