Maybe you’re right. Maybe the world just had a bad year.
Still, I don’t think it’s crazy to challenge applying ordinary flu metrics to a strain that killed an extraordinary number of people.
no, it wasn't just a bad year (although definitely the conditions imposed by ww1 had a lot to do with it), it was an exceptionally deadly strain of influenza. but it was still an h1n1 influenza virus and probably behaved similarly to other h1n1 strains in matters other than how virulent it was.
like if all the influenza strains that currently circulate, which are collectively much less closely related to each other than the spanish flu strain is to current h1n1 strains, fall into the frame of 1-4 days incubation period, mean 2 days, then it seems likely that the spanish flu also would.