Sure call it silly, but below-average (even by a point below a school's matriculant mean MCAT) puts you at a disadvantage. Also, many other DO schools have averages higher, so unless you're only applying to ATSU or schools with MCAT averages at or below ATSU's, then you're going to be below average for every other DO or MD school you apply to. Let's be honest, a sub-504 is not THAT competitive even for a DO applicant, and you know that. Of course you can get into ATSU or wherever with a sub-504 but your chances go down when you are not even at the school's average; hence a retake is recommended if you have the ability and confidence to score better. Also, trends for many medical schools have shown MCAT score increases every year, so a 504 may not even be this year's mean matriculant score amongst matriculants with a score on file.