To answer your questions, jjg2, I did withdraw from the prelim year match since you have to commit to these pre-residency fellowships before the intern year match. Whether this is a red flag is debatable. I can say that I went on about 10 prelim/TY interviews the second time around, and at each interview I was asked about my confidence in performing a physical exam, obtaining a medical history, etc given that I would be a year out of medical school before starting internship. Despite explaining to these programs that I had already registered to take USMLE Step 3 to beef up my medical knowledge prior to starting internship, and telling them that as part of my fellowship that I performed medical histories and physicals on pre-op patients, I still fell quite a bit on my internship match year list. So, I can say that for me at least, taking a year off hurt me with regards to matching into internship year, but that may not be the case for others.
You have to put it in perspective though. I would gladly do a pre-residency fellowship and match into the most god-awful surgery internship in Timbuktu, if it meant that I got to do ophthalmology in the end.