Completely agree. Adding a proper primary key e.g. from a sequence involves very little extra overhead and protects against this. Asking them to drop the constraint in the future sounds a bit silly as that may mean two members get deleted when you intended only one. Plus your foreign keys now have to be maintained. So if a member changes their name you have to update all foreign keys. Also if the hobbyist club then builds a website to view members the URLs can use the primary key e.g. a long / bigint, rather than names. The names may introduce further complexity with having to escape the URL etc. I am all for keeping it simple, but all relations should have a guaranteed unique primary key.

I know the author is talking about a small scale project here, but shortcuts like this (in my experience) just lead to a mess later on; irrespective of the complexity of the problem being solved.