Most statistics is estimates and approximations, as far as I can tell, Russian official economic figures are generally seen as relatively reliable, considering the environment.
For example, people know that exchange rate is influenced by currency controls, that you can massage inflation and employment numbers to a degree, but you have the overall context. When the official inflation rate is not moving, and the central bank is leaving the rate unchanged, after both rates was previously going up, you can deduce that inflation is under control.
You cannot completely fabricate the entire picture, you have stock exchange where local people invest and they would have a pretty good picture of what is really going on. And Russia's economy is probably watched closely enough to be difficult to just pull figures out of thin air. There is considerable revenue from oil which is fairly obvious to see, and we don't know how much money, which was being stashed away for years for topping up pensions and price subsidies to keep to people happy now being poured into war economy.
It's a reasonable assumption this would help any economy in short to mid-term plus the blood money for the families. Buryatia for example must be now basing its entire economy on blood money, with population of less than a million and my estimate of having at about 2,000 dead in Ukraine.