The fancier rippers have testing and database for calibration of each model of optical drive. Basically, every one can have a different offset of a few dozen samples that you probably wouldn’t miss*, but if you compensate for that you can match checksums with other people ripping the same disc and know that you have an error-free rip.

*If you are ripping continuous DJ mixes with track markers, you also don’t want that gap of missing samples.