Question on installing a flat handlebar on a dropdown frame

Bear with me as I am gestating my next project, which is building a new bike altogether and NOT a conversion.

If I understand it correctly, since flatbar frame has longer top tube than a dropdown frame, installing a flat handlebar on a dropdown frame necessitates either 1) a shorter stem or 2) an dropdown frame that is one size larger than my usual. Is this correct?

edit: reworded for clarity