so this shouldnt need explain to anyone but 538 is generally fairly terrible when it comes to being able to predict the playoffs. playoff match ups are simply too big of an issue for algorithm based on regular season game play to be taken as more than general information.
but furthermore in regards to the G's, 538 REALLY REALLY doesnt like them. Right now there are 7 teams (maybe 8 if you squint) teams in the AL fighting for the playoffs (O's are the squint team), and 7 teams in the NL. Of those 15 teams, the Gs are ranked 14th (only in front of the O's) and that includes the white sox who the G's are currently 4 games better than.