I would not describe my undergrad record as being "subpar," but it was definitely impossible to evaluate in the normal sense b/c of there being no grades, GPA, or credit hours for it. So I don't know if my experience is really what you're looking for, because I'm honestly not sure whether the schools considered my undergrad record as a "blank slate" that they mainly ignored, or whether they saw it as a "subpar record" that I had overcome with a strong graduate record and MCAT score. But FWIW, I was offered scholarships at a few schools in spite of having no undergraduate numbers whatsoever.
Edit: Just to clarify, my undergrad transcript is basically a list of the courses that I took and passed, in random order. So the med schools can see, for example, that I took something called General Chemistry with lab, and that it lasted two full semesters, but that's the only information my transcript provides. The medical schools would have no way of knowing whether I took one class per semester or twenty, which classes I took when (and my college did let us skip pre-reqs with the professor's permission), or even whether I had failed a class. I didn't ever fail any classes, but if I had, the college simply would just not list them on the transcript, and it would be like those classes never existed.
That being said, we did get narrative evaluations, and I copied the ones for my pre-med courses and sent those to the med schools. The NEs explain what we covered in the course, and describe my performance and my work ethic. (It's funny to go back and read ten years later that my professors were all so impressed that I always came to class and turned in my HW on time!

) My NEs ranged from saying that my work was average (physics, biology,) to above average (biochem, literature) to saying that I was the top student in the class (calculus, gen chem, organic). It's kind of like every prof wrote a little LOR, some of them painstakingly detailed down to how I performed on each question on the final, and many of them a bit too critical for me to enjoy showing them to outsiders like med school adcoms. But they are all I have, so....