Are there histones present in the cytoplasm?
In early embryogenesis, cell division called cleavage occurs every 30 min and there is no transcriptional activity. Oocytes have accumulated important gene transcripts and synthesize the proteins at right times. However, histone is one of the most abundant proteins and it would be difficult to supply enough histone proteins during early embryogenesis while oocytes translate other gene transcripts regulating differentiation.

This is my speculation, but the article calls cytosolic histones "stockpile". Just in case, I don't mean that I deny some other roles of histones in cytosol if there are any.