

That’s just pedantic, you will always need to know where the door is to enter the network, but in both cases even if that specific server that you know gets taken down you can still enter by any other server you might discover in any other way. It doesn’t cease to be centralized because you are using the same single node to get into the network, that would be like claiming email is not federated because you only use Gmail, or because you need to know the email of the person you’re writing to.
It’s still a decentralized system, and saying that they aren’t because the default is for everyone to use the same node is either disingenuous or missing the point entirely. By your definition decentralization is impossible, because you always need to know at least one node in the network in order to enter.