- the 3550/4550 line of drives are picky scanners (mostly over-reporting)
- the scanning graph you get in the 3550 is excellent
- the TRT in the Sony looks fine despite the awful PIF figures, which is suspect
...it seems probable that indeed something's wrong with the Sony DL scanning.
Another possibility is that the Liteys (the Sony is a rebadged LiteOn) don't like NEC DL burns for whatever reason. I wouldn't be the first time that such peculiarities are observed.
In my personal book, if the scan looks fine in a 3550/4550, the burn is OK. I distrust these drives as scanners because they tend to show far too many errors, so if they're low I'm good.