Let me give you two concrete examples of path performance of a good and a bad path. For simplicity, we will consider that: whenever a link is bad, it has a loss rate of 10%, which is above the 1% threshold we mentioned before; whenever a link is good, it has a loss rate of 0.1%, which is below the 1% threshold.
We consider the case of path $p_1$ being good or bad based on whether $l_C$ is good or bad. Links $l_1$ and $l_2$ are always good here. Let us take the case of $l_C$ being bad. Then, the loss rate of $p_1$ is 1 minus the delivery rate along the path. As said, $l_1$ is a good link, so it has a loss rate of 0.1%, i.e., a delivery rate of 99.9%. $l_C$ is bad in this case, so it has a loss rate of 10%, i.e., a delivery rate of 90%. So, when $l_C$ is bad, the loss rate of $p_1$ is around 10.1%.
If we were to do the same calculation for the case of $l_C$ being good, we would arrive at a loss rate of around 0.2%.
So based on this, you see that these two numbers, 10.1% and 0.2%, are far apart.