Engel's anarchism = socialism.
Anarchism: Absence of government and absolute freedom of the individual, regarded as a political ideal.
In other words, voluntary interaction. Certainly small socialist "groups" can form under anarchy, if the members of the group join into a voluntary contract, but these groups do not define the broad term "anarchism".
How do you avoid privatized production in Engel's anarchistic state without force? You cannot... you must rely on some authority with the right to initiate force to compel everyone to comply, therefore it is not anarchism.
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