If your Read Transfer testing drive reads even really bad discs with no slowdowns at all, then it is useless for testing because it never tells you when a disc is bad.
You can't ask Stephen Hawking whether your thesis on black holes is too complex for regular people to understand, because he'll be able to understand any theory you can come up with.
This is the equivalent of "too good reading drive".
You also can't ask an idiot with an IQ of 20 the same question, because he will not be able to understand even the simplest of explanations.
This is the equivalent of "too bad reading drive".
That's why I say that your Read Transfer test drive (if you only use one) should neither be too god a reader nor too bad a reader, because you will get meaningless results!
A couple of each. Some were generally unreadable except perhaps with great difficulty in a single drive, and some were only problematic in a single drive.
Since one main purpose of burning media is that it should be readable in any drive, it's simply not good enough if it fails in one type of drive (unless that particular drive is defective).
I don't care how few PIE/PIF a scan shows, if the disc isn't readable. A disc like that is useless for all purposes, except for bragging rights in one of the "hall of fame" or "dare" threads on the forum!