18.5" of upright downtube (as frame sizes were measured in the 80s) looks nothing like 18.5" of compact frame. Maybe I should explain that at the time the trend was to have as little stem coming out of the frame as possible because it was believed that it made the bike stronger.

It was a lightweight tourer, and it was the smallest size easily available for a real adult bike suitable for commuting (not a shopper) at the time. Could get off and on safely as the top tube sloped v steeply and finished lower than a mixte frame. Until it got stolen <sigh>