On Genuine, quality media, it can have the opposite effect. On good media you should burn it at its rated speed you will get a better scan. Remember, high speed media uses a special dye that is more sensitive and requires less exposure to the laser, so it is better to burn that way.
Example, I always burn my Taiyo Yudens 8x at 8x, whether data or video, I have posted some scans in other threads, they are excellent. Burning it at 4x would give a higher PIE/PIF count.
There are some cases of crap media rated at 8x that burn better at 4x, but for quality media burn at its rated speed. For 16x media, I would burn at 12x.