The TABLE statement in this PROC TABULATE step has Year as the page dimension. Therefore, PROC TABULATE explicitly produces one page of output for 1995 and one for 1996. ODS starts a new body file for each page. 
proc tabulate data=grain_production format=comma12.;
   class year country type;
   var kilotons;
   table year, 
         country*type, 
         kilotons*sum=' ' / box=_page_ misstext='No data';
   format country $cntry.;
   footnote 'Measurements are in metric tons.';
run;