Since the expert did not answer in essence (it is not clear from the answer whether the quality of Russian generics is worse or not), then for completeness I will add: my good friend pharmacist categorically requires me to buy only drugs produced by well-known European companies (such as Bayer-Henkel), and avoid Russian and Indian generics. Although, of course, this does not pretend to be an expert answer.
Both European and Russian companies buy raw materials from Southeast Asia. There is not a single chemical production of substances left in Europe. Moreover, in European countries, many drugs are cheaper than in Russia. Naturally, this does not mean that medicines are made there from low-quality raw materials. In most cases, the price of a drug does not depend on the cost of raw materials at all. The main share is spent on the brand: salaries of medical representatives, display advertising, promotion in pharmacies.
Ideally, for a generic to act in the same way as the original drug, a set of requirements for the raw materials from which they are produced should be same. This is not controlled in Russia; raw materials can be produced using different technologies. This, in turn, leads to significant or insignificant differences between the analogue and the original.
As for additional purification, the concentration of not all impurities in general is controlled, but only certain ones. Cleaning is carried out, among other things, in order to bring raw materials in accordance with state requirements. No requirements, no cleanup. No company - Russian, German or American - will perform additional technological operations if they are not required.