Dry sift vs BHO

So I've been watching videos of guys "carding" kif over mesh screens endlessly in an effort to get pure trichomes. The before pictures definitely show a lot of plant matter whereas the after pics look like nothing but heads. Looks killer but a shitload of work.
My question is this: when I run BHO, is the final product closer to pure heads or is it loaded with contaminates like the initial couple screenings when dry sifting? We use a 95 micron screen before the honey pot? I have looked at my bho and never noticed plant material like the initial dry sift photos.

I think BHO is mainly the oil contained inside of the trichome heads. As far as contamination, some people will filter to as low as 1 micron... some use coffee filters which are around 25 micron. Im still using coffee filters at this point, and a few specs manage to make their way through to the collection pot from time to time.