[Mumbles something about hormesis.]
If the virus replicates more slowly, a large infectious dose would have the same impact as multiple replication generations.
I'm not asserting the above is what happens, I'm asking the question.
The Vmin to be detected by your immune system is small. You want the most time between Vdetected and Vdanger.
Some guy vomited in a restaurant. Then you can clearly model the time from exposure to symptoms in everyone else based on how far away they were when the guy vomited. Though in this case the viral exposure was very high for everyone in the restaurant.
For influenza, each infected cell apparently infects ~22 other cells:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1563736/
So in 2 generations you have 500x the virus.
If it were 'less' exponential, and each cell only infected, say, 5 others, then you get to 500x late in the 4th generation.
In a cartoon example where a low exposure leads to 1 infected cell and a high exposure leads to 500 infected cells, the low exposure matters more if the reproductive factor is lower.