True, if using something like “current upload + 1” the progress would potentially be small - but still not likely negative which is what the current default of 1 gives us. But you’re right - if done from the start it would indeed simply verify what was just uploaded. 
According to @kenkendk from another post…
That’s a tough one. I suspect some backup software falsely inspires confidence by doing no (or minimal) testing - thus never finding errors leaving the user potentially stuck when things can’t be restored.
For me, I feel more confident because of the fact that Duplicati actually found something. Sure, something went wrong and I have to deal with it - but I get to do that on my time instead of after an emergency when I may realize I can’t restore things I assumed I could.
But I agree with the unclear significance of the error. Even with kenkendk’s description it’s still not really clear what a user should do about it.