Of course this is possible, but much harder to pull off logistically. It's far less likely that someone will dump in the grand finale after playing months of playing dailies just to qualify for the finale - dumping to someone in a daily (especially once that person is out of contention for 1st in the overall standings) is far less of a loss to someone than it would be for them to dump in the finale.
And also dumping to someone in one tourney certainly does not guarantee that person victory in that tourney - the variance is obviously quite high in that regard (naturally it would help them but far from guarantee them 1st), whereas if someone gets dumped to in the dailies on a consistent basis, that would definitely give them a huge edge in regards to finishing higher in the overall standings to someone playing it straight.