Earlier quoted context omitted.
This isn't accurate.
Wiki article on the Toba Catastrophe theory. Sparks Notes: - It is thought that the Toba Super-Volcano eruption is linked to a severe drop in human populations due to it's influence on global climate - Some genetic evidence supports today's humans are descended from a very small population of between 1,000 and 10,000 breeding pairs that existed about 70,000 years ago - This hypothesis isn't yet solid, and there is so…
A bottleneck implies that there was a single population, which would indeed have narrowed diversity. ...but what is actually seen in that theory is that all populations around the world shrank - only some were entirely exterminated.
This means that diversity was not tremendously impacted.
Taking one person from every village around the world preserves the majority of all diversity, whereas taking 10000 people from a single population, destroys diversity.