Haydn's Esterházy orchestra was 13-24 players in size, what we might often consider a chamber orchestra today. The bloat--if that's what it was (Wagner and Mahler would disagree)--happened later. AFAIK, Haydn wrote more symphonies than anyone else, so if he's not symphonic, who is?
Sad day when Spector has to be invoked in talking about chamber music and symphonies.