aside from massive manipulations, at the taking and printing stage, i would suggest that the survey work osullivan did
for the federal government, if printed in the same "full scale" way ... if osullivan had film and enlarging paper / instead of
a tent filled with ether fumes, glass plates and cyanide ... ( to me at least ) maybe they would look pretty much the same. AND if osullivan
was shooting dry plates instead of wet plates, he probably would have been using the system a lot of people used to manipulate
a negative at the taking stage to get a full scale negative, which adams renamed the zone system, and people mistakenly think he invented.
whether he had a bunch of people running around with him saying " photography should have everything in focus ( + HDR bla bla bla the rest of the f64 manifesto )"
i don't really think is important. if you have ever seen some of osullivan's giant plates you soon realize he was probably every bit of an (anal retentive) perfectionist as adams was ... his subject matter was similar ... and well, adams and him kind of sort of shot in the same vein.
i haven't seem much of osullivan's portrait work but i am guessing since he was also a portraitist ( from what i remember ) his portraits were
probably stiff, mainly because of the materials, while adam's portraits were stiff because it seemed to be more of a stretch for him.
getting back to the questions though, neither adams nor osullivan were shooting in a vacuum. they were both professionals, and well connected ....
and would have easily known what others were up to, whether those others were dead or alive ...
it is hard to imagine someone, even someone learning photography in the 1850s and in persia, doing it in a vacuum ...