Survivorship refers to people that engaged in an activity with a chance of "survival" (which could mean actual life or death situations, or things like interviews, school applications, etc.) and did survive have a biased view towards the probability of surviving that activity - usually overestimating the chances of "survival". A classic example is that you might not want to trust it when a professor in a competitive says success in the field is likely with hard work - sure, the professor may have worked hard and succeeded but he's biased towards his own experiences, and is likely not making an honest assessment of the chances of success. Survivorship bias is a form of selection bias: the "survivors" are essentially selecting their own experiences over that of the general population.

Whereas selection bias is when some external factor causes analysis to be focused on a specific subset of the broader population. For instance, survey responses reflect the selection bias of people who were willing to take that survey. Reviews on user-generated review sites are biased towards the people that felt strongly enough to leave a review. The example in this post is selection bias. This is not the opinions of views of individual survivors as in survivorship bias. Rather the study is inherently limited to selecting those that were healthy and fit enough to survive the Holocaust.