What ChessIQ is measuring
ChessIQ is not trying to guess talent or predict your rating. It measures move quality in context: what the position allowed before your move, what changed after your move, and how large that swing was.
Move labels (such as Best, Good, Inaccuracy, Mistake, Blunder, or Miss) are readings of engine evaluation data. Accuracy summarizes decision quality; it is not a full description of everything that happened in the game.