That is not so much an assumption as a conclusion, backed up by research:

https://urban.uw.edu/news/crows-hold-grudges-against-individ...

https://crowlingo.org/journal/marzluff-mask-experiments-expl...

I think the person meant that it might not be for the mask-wearer. They might be targeted by crows even when the mask comes off because the crows might still recognize them from their walking style or body odor or voice etc.