This is quite ingenious. I once witnessed a website that was attacked. They called it a Ddos attack and they advise that people login with the mirror site. Was quite confused, I think i understand better now, the importance of mirror sites.
Well, same name, quite different purpose.
Hive has such functionality built-in, you can see my post in:
hive.blog, ecency.com, peakd.com, or even in many block explorers such as hiveblocks.com, or hive.ausibit.dev
Every Hive node has a copy of the network.
However, a Mirrornet (a.k.a. fakenet) is a concept of a disposable clone, that can be used for experiments without the risk of affecting the original.