This is an interesting article, but I think most of it does not seem applicable to a reasonable civilization attempting colonization, that is aware of these problems.

  1. The population size in the colony will be very small. Maybe? It should be at least MVP (minimum viable population, not product) that is a relatively well researched concept. I'd argue that it won't be a colony below that. More of an outpost. And when talking about aliens and Fermi paradox, we don't even know what their MVP might be. It may not be even close to MVP of vertebrates on Earth.
  2. That selecting the colonists by some criteria is not useful. It is, it's just not selecting by the "best genes". It's selecting for more diversity in the first place. Lack of diversity in the colony is much less of a problem, if more of it is introduced in the first place. 
  3. That colonization is an isolated thing and people won't arrive/leave over time. Why wouldn't there be more than one colony ship, if sending them becomes viable overall? 
  4. The population does not grow and remains at the original diversity levels. Combined with 2 and 3, it may not even matter that much. Unless it experiences a series of catastrophes, it should keep growing and becoming more diverse over time again. This is of course the most questionable case. Will it? I think considering how humanity has spread like a plague on Earth, it won't be a problem.

What I think is that the table might look very different with the above taken into account. Maybe 99% of diversity in the first colony and none of it will necessarily remain static or diminishing.