Without speculating on Forever 21 or how this particular product ended up in the boxes…
My company previously partnered with a marketing “value add” company that sent us promotional materials to include with our shipments. These weren’t put in the boxes at pick time, they were inserted en masse much earlier in the process. So, when the pickers in our FC (fulfillment center) did their thing, there was no “choice” about what items were included with what orders.
After a few campaigns where the marketed goods/services were in direct conflict with our brand (and our parent org), we discontinued the partnership.