This makes zero sense. If power is concentrated, then it doesn't represent workers interests. If it represented all workers interests, then power would be diffused.

The person you're responding to's description is slightly wrong. A "People's Republic" defines a Socialist state who's government is made up of an alliance of parties, rather than a single communist party, and that United front government might have parties intended to represent sections of the national bourgeoisie. So there's a nominal Power sharing element here.

That said, I'm not sure how it logically follows that a state which represents the interests of workers must therefore be decentralized in some way? These places often end up with centralized political systems (though the list of States OP gave is full of a whole lot of variety in their institutions and political cultures), because of outside influence.

The DPRK is like that because some white guys drew a line across a country, and them bombed it until pilots complained there were no more targets to bomb, and civilians began living in caves. The DPRK (and the ROK for that matter lbr) has been something of a basket case ever since. But that's because power centralization is a response to material conditions, not a result of what someone named the country.

How are these one-party governments, gauging the interests of their workers? How are they doing this without democracy and voting? Afaik these countries don't even ask their citizens for feedback

People's Democracies are defined by the presence of multi-party systems, like I explained earlier. Though these secondary, non-Socialist, parties have greater or lesser degrees of importance depending on what country we're discussing.

That said, there are all kinds of institutions by which a people's democracy gauges the interests and feedback of the workers and other represented classes.

I'm going to talk about China, even though it wasn't referenced in the OP, because it's a People's Republic, and I can speak to its institutions with the most confidence:

One way class interests are gauged by the state is through the party system. This doesn't matter so much in the primary legislature, the National People's Congress, because the allied parties have a small fraction of the seats, but the NPC is historically a rubber stamp for the much more vibrant, body, The Chinese People's Political Consultative Conference (where the communist party only has 97 seats out of 2,169), where various sectors of society are represented, including parties, ethic and religious groups, organisations in the arts and sciences, mass organizations that represent women or young people, trade unions, etc.

In all state owned enterprises as well as in large parts of the private sector, there are a network of Workers Congresses which allow workers to engage in firm management.

There are also Party Committees in many workplaces, where the communist party itself plays a role in firm governance. These institutions make sure private companies follow the five year plans set out by the state.

There are also trade unions, which represent workers interests in other ways, and have representation in government.

There are also an extensive amount of Worker, Consumer, and Agricultural Cooperatives in China you might find this interesting, as it speaks to your concerns about decentralization. Between State Owned Enterprises, and the private sector that the state is always trying to reign in, co-ops straddle the line between these, by being worker owner and run firms, more independent of state power, and not beholden to the interests of capital like a private corporation.

People are often (sometimes rightly) critical of the privatization of the Reform and Opening up period. But that capital inflow has allowed China to turn around and invest in a domestic cooperative sector that rivals private capital. Huawei is the largest telecoms company in the world, for instance, and it is a worker co-op.

So there are lots of ways that's workers interests are guaged and turned into an economic plan that will benefit them. Obviously, these institutions have been more or less effective at different times, or in different parts of the country. And a the Chinese system isn't universal (The DPRK or former East Germany looked a fair bit different to this. While modern Vietnam or Laos modeled a lot of their own reforms off of China), but hopefully it gives you some insight.