Forgive my ignorance here but how do you know this is one miner. The right hand column of your link says "unknown blocks" and almost all of them are single recipient IP addresses. I just assumed this bucket made up the 15% of the network that didn't join a mining pool.
You're right they are going to different IPs, but IPs don't actually identify users, it's very easy to clone them and use proxies.
I have heard that solo mining is useless unless you have a ton of network power. That makes it seem likely the unknown section is not made up of a ton of individuals but is like a private mining pool from just a few locations.