Yeah its doing something to measure the angular velocity which gives some idea of the density of the recording. I guess its doing this via read seeks, maybe Reentrant has some further insight on how it works and translates to the tables it makes.
I've never had issues with it on CDs, only bugs on certain dual layer DVDs like GTA IV and Supreme Commander.
Can you check how it does the error stuff with that Skidoo discs, it has a way of dealing with the errors where it doesn't hang infinitely. No other tool I found can do this.