Check out evaluateDetectionPrecision. which is same as you mentioned about detectorPrecisionRecall. you must have seen that this function are widely used in the object detector examples, its because the output you get from these functions are "precision" and "recall", the two important performance metric which is nothing but sensitivity and Positive predictive value. You can use these metric to calculate almost all important performance criteria. Thus you may not need to use confusion matrix at all.
I hope this clear your confusion.
Cheers.
