That's not what the parent comment is talking about. Berezka stores were originally created to earn dollars by selling Soviet wares to tourists, and later gradually reoriented towards the few Soviet citizens who earned dollars and looked for some way to spend them. Not to be confused with other special stores unavailable to ordinary citizens that supplied party members.

What parent comment is talking about was the system of cash and cashless (безнал) roubles. Cashless roubles were used for industry purposes and couldn't be converted to the ordinary roubles available to the population. When USSR allowed cooperation (primitive private business) in the late 80s, it was used by many officials as a tool to convert the cashless roubles from the organization's they controlled into real currency in their private pockets. And a lot of oligarchs (including Khodorkovsky) got their fortunes that way.

It's ironic that now ordinary Russians blame the chaos and injustice of the 90s on capitalism and free market, whereas a lot of that was created by a state economy system and exploited by corrupt beurocracy of a communist party.