I think they are confusing something. A "captain" (in Russia they use the term "brigadeer"), an analogue of the "capo regime/capo decina", in the Russian crime organizations, doesn't necessarily wear tattoos, it's just a position which he gets if appointed by the boss.

While the tattoos and the risk of being killed if they lie about their position, this concerns the status of "thief in law" instead. If somebody says he is a thief-in-law (vor v zakone) and then it turns out he isn't, he most likely will be killed.

Thieves in law are a different thing than "brigadeers" and other hierarchical positions though, they rather indicate a sort of "special status" of "respect" in the criminal world, like the upper caste in the caste system in India, the criminals who are generally most respected by other criminals and can have the last word when solving disputes, if agreements can't be reached, have a special status in prison etc. But thieves in law aren't necessarily mafia bosses, they can be leaders of small gangs of robbers, they can even be pickpockets (at least until not so long ago).
They were formed during the earlier years of the Soviet Union, when the mafia in the modern sense of the word didn't yet exist in that country, due to the lack of possibility to make money as independent businessman, there were no private firms and companies, I mean somebody couldn't become a successful businessman or like the today's "oligarchs", since everything was controlled by the state. I mean, the only "mafia" existing back then was the Communist party itself, if we use the term "mafia" in a more wide sense of the word.

While racketeering, extortion of businesses, control of "cash flows", money laundering, all this appeared only at the end of 80s, when more economy freedom outside of control by the state was allowed. Before that, there were gangs and thieves in law, but the only economy they could control was the "black market" by directors of various fabbrics, state institutions who were making money on the side, like for example, when they were provided more material than was needed to priduce a specific quantity of goods requested by the state rules, so they produced additional things with the remaining materials and sold them, without reporting this additional income. Sorry, the economy isn't my strong side, but anyway, the point is some financial operations, even those legal today, were considered illegal in the Soviet Union, so only "illegal" businessmen existed, and they were the only possible targets for large-scale extortion. Since they did money in a way considered illegal then, they couldn't report the extortions without ending up in jail themselves, so that made them easy targets. However, extortion/racketeering was first introduced in the first 70s by Gennadiy "The Mongol" Korkov, who wasn't a thief in law, and his new way of making money was initially even met with distrust by the thieves in law. However, later they understood the profit and when he was sent to jail, they gave him a thief in law status. Vyacheslav "Little Japanese" Ivankov, the thief in law who did prison time in USA later, started in the "Mongol's" gang.