I think you have illuminated the crux of the non-existent issue :-) At 97% reduction, even a virus with extraordinary replication speed is significantly hindered. The replication would need to be 1/(1-0.97)=33.33 fold to negate Brilacidin. I'm not sure the transport mechanisms available can even expose enough cells to support replication anywhere near that, otherwise the lethality would be crazy fast and it's not.
Obviously I'm out of my realm but you may have helped me connect the dots. Let's see. Forgive me if I'm saying pretty much the same thing you just posted (btw, I hadn't seen it expressed this way before now).
If, at the point in time that the results were measured: 1. The viral load in the untreated culture was X + Y. 2. Then the viral load in the treated culture was .03(X + Y).
Is that it? I think that equation mathematically says that Brilacidin reduced the viral load in the samples 97% more than nothing at all did. And that's finally starting to sound more meaningful to me.