That's not what "rent seeking" means. Imagine you have a bench on your property and people can just rest there. One day you start charging money for it but without offering anything extra, same old bench. That "squeezing for money with no justification" is "rent seeking".
It's not like that. They buy mcnichol.com on your behalf, when you request it. They're not registering it in advance and then blackmailing you to rent it through them. Domain is yours, you can move it elsewhere (they explicitly mention that).
It's same as any other domain registrar, except that have small markup (couple of dolars per year) but they provide additional service, i.e. customer doesn't have to deal with DNS.
