This mixes up accuracy with precision and 538 had written at length about this. There's a big difference between pollster bias correction vs rating. There are

This mixes up accuracy with precision and 538 had written at length about this. There's a big difference between pollster bias correction vs rating. There are many pollsters that are pretty consistently +2D/R but are reliably off from the final result in that direction. These polls are actually extremely valuable once you make the correction in your model. Meanwhile, polls that can be off from the final result by a large amount but average out to about correct should not be trusted. This is a yellow flag for herding A pollster can have an A+ rating while having a very consistent bias in one direction or another. The rating is meant to capture consistency/honesty of methodology more than result