It's not like Russia is a closed country, nor is inflation difficult to measure. Third parties don't simply take Russian figures at face value, which is why the numbers from e.g. the World Bank will vary slightly from those of the IMF and then vary once again from the official figures, and so on.

When the Russian economy was briefly under substantial strain when the huge sanctions attack first landed and the ruble fell rapidly, not only did their official numbers reflect this, but they had a more negative expectation than third parties!

For that matter there are a zillion videos you can watch on YouTube of people doing walking tours through various supermarkets and places looking at the availability/prices of stuff. Here's one from some lady a month ago that clearly leans ideologically Western, but nonetheless affirms prices to be somewhat lower than would be expected from the official rates, while complaining about it - https://youtube.com/watch?v=m01-iYSPDt0

Made even sillier if you're aware of Russia's economic history since the end of the 90s. Their economy has for decades been seeing substantial inflation (5-10%) yet even more substantial wage growth. So complaining about prices without even mentioning the change in wages is the sort of behaviour one should expect from people of this sort of bias.