When the length of the iterator is 1 or 2 the progress bar is not printed at all:

julia>  @showprogress for i in 1:1; sleep(1) ; end

julia>  @showprogress for i in 1:2; sleep(1) ; end

julia>  @showprogress for i in 1:3; sleep(1) ; end
Progress: 100%|██████████████████████████| Time: 0:00:03

For consistency, I think that a progress bar should be printed in any case at the end of the loop no matter what the length of the iterator is and also no matter how large/small the dt option in the progress bar is.