The indefinite in «إنسان لم يقم» may be analyzed with regard to some members of a class or the nature represented by ‘human’. Confusing these possibilities obscures what kull adds.
If the earlier sentence reports the non-standing of an individual, adding kull extends the attribution to every individual and establishes additional meaning. If the context already conveys universal distribution, kull may instead reinforce it.
The goal is neither to force one logical paraphrase on every context nor to erase the genuine alternatives identified in the discussion.