It makes sense from his point of view legally, but at an emotional level it conflicts with the open decentralised ethos of the Fediverse, where no one owns the network.
This is just a guess, but I don't think most people realise that the work "mastodon" is a trademark owned by a central legal entity?
The good news is you can avoid all this by choosing a domain name that doesn't mention that word.
@homegrown most people even don't realize that mastodon ≠fediverse :(