My own interpretation of the definition of decentralized as it pertains to technology would also imply there is not a single super-node you have to boot-strap from. One should be able to host their own boot-strapping cluster of nodes so that if a company goes out of business their nodes will continue to work, software updates not withstanding.

Not depending on a single node to me sounds more like distributed like Tor or clustered like Ceph or in some cases federated like Mastadon or Matrix.

Not sure I understand. Should you trust Silk in this case? Wouldn't any issue with this company mean unavailability to everyone's data? Maybe i have missunderstood the producy