The iHAPx22 W drives may be a close relative to the iHAPx22 9 drives, but have some unknown change in hardware. It is a bit different, however, from the iHASx24 B lineup, which could explain things.
Here’s a link to the FAQ that gives a general overview of what HyperTuning is: http://club.myce.com/f44/f-q-liteon-optical-drives-revised-16-june-2009-a-109986/#HTOS
…And with such an option, the drive will check the media periodically throughout the burn and adjust laser power if necessary as it learns. This could result in a lack of noticeable rings.
I would like to point out that the rings are nothing to worry about. They are normal (though they may not happen with every disc & on every drive). Like mentioned above, it is just the drive tweaking the laser power a bit as part of whatever writing strategy it uses, and can occur even when a drive does not use Z-CLV to burn media.
The only time you should worry about “rings” is if you have discs that can’t be read because the drive did a bad job of writing a certain part of the disc.