There is really no way to know. Mining pools do not publish where people are mining from so all you can see are the pools.
Even if the pools did say where the work was coming from it would be a guess at best. They only know the IP that the work came from between VPNs & proxies it would be a general guess at best.
I think we can safely assume that the vast majority of miners don't mine behind VPNs, and the map provided in the OP goes in line with the study from
Cambridge, and I believe they use the same data since the numbers look pretty similar, you can read more about the "data aggregation and analysis" they used
here, but long story short, they get these data from (BTC.com, Poolin, ViaBTC, and Foundry) and separate it by IP addresses, the last update was April 2021 when those pools made about 35% of the total network hasharate, while you can't take this info to the bank, I believe it's accurate to a fine degree.
Of course, with the recent shutdown in China, these figures must have changed a lot, but at least at the time of posting them, they were fairly accurate.
