I think there may be a difference in measurement and that might where the discrepancy is. According to Wikipedia's entry on optical drives:

The 1× speed rating for CD-ROM (150 Kbyte/s) is different from the 1× speed rating for DVDs (1.32 MB/s).

So if that was indeed a 2x DVD drive, it would be pretty comparable (if I'm interpreting all this info correctly): 16x150,000 bytes per second= 2,400,000 or ~2.4 MB/s and the 2x DVD speed would be 1.32 MB/s x2= ~2.6MB/s

Pretty close!