Is this a place Sony could differentiate from other platforms?

Contractually require (and technologically support) that the servers are kept running for n years after the last sale, for example?

This week a Microsoft representative told Congress that all Minecraft servers except the ones sponsored by Microsoft are illegal piracy.

It was a trade association not Microsoft. And bullshit like this is the entire reason for trade associations existing.

Microsoft themselves support self-hosting Minecraft servers. As evidenced by the fact that the server software itself is provided as a free download from an official Minecraft (and thus Microsoft branded) site.