The intention of this is to get tax revenue from the large transactions. But it will be complex for the gov to verify if the transactions were made by Russians or in a Russian exchange.
The intention is good, I mean, any gov wants to get their taxes but the technical problems will come when the Russians use an exchange from another country, I think it will be a complex task to trace all the bitcoin users on Rusia and keep an eye on each of their transactions.
You are right it may be complex for the government but as we know now most of the exchanges ask for KYC so the government can ask the details if these external exchanges are operating their service in Russia. The people will also not hide after using these exchanges because they will know that there will be a penalty if they break the rule of government.