Is it actually a penalty, or possibly loss of a 5 "point" ranking factor boost that's no longer worth that 5 "points" so it's discarded and reflects the total scoring and the consequent drop
jd did a good job of explaining why this wouldn't apply. But again, the instances of finding #2's and #3's stuck exactly at #6 seems to imply a "you're good enough for the first page, just not the top 5 listings(but not bad enough to be below #6)".
Otherwise would be seeing results scattered to #4, #7, #11, #13, etc. according to the "less credit" theory.