I wasn't contesting that. I was just correcting your assumption that the placements were arbitrary.Yes. However, if I understand it, MLG uses further rounds and matches to determine 5th, 7th, and 10th place.
http://www.mlgpro.com/pro-circuit/2010/
Thus, it is possible to determine 5th place accurately. That is, as accurately as tournament results can determine any placing. Thus, who got 5th is as accurate as who got 6th.