Workers had no control over the means of production. Those were owned by the party which was just another form of bourgeoisie rule. A good example of that was the insane amount of nepotism in the party leading to appointment of friends and relatives with no competency who went against the wishes of the workers. Trofim Lysenko for example was appointed by Stalin and his policies forced farmers to basically kill their crops leading to mass famines in the USSR and those that didn’t were declared fascists, traitors or something along those lines.
It’s not socialist if the workers lack any control.