According to Introduction To Probability by Blitzenstein and Hwang p. 244, one example of length-biased sampling is the following:
"For example, asking randomly chosen mothers how many children they have yields a different distribution from asking randomly chosen people how many siblings they have, including themselves."
This seems like an instance of the class-size paradox. How is this also an example of length-biased sampling given the definition from Wikipedia
"Length bias is an overestimation of survival duration due to the relative excess of cases detected that are asymptomatically slowly progressing, while fast progressing cases are detected after giving symptoms."
I'm not really seeing the connection.