AFAIK not entirely true. It has been reported on the S2s and a few VT20s. Please have a look at these threads here.
http://www.avsforum.com/avs-vb/showthread.php?t=1236475&page=7
http://www.avsforum.com/avs-vb/showthread.php?p=18361224#post18361224
http://www.avsforum.com/avs-vb/showthread.php?t=1236475&page=10
Some people noticed it after a few days, some did not see it and some that compared the G20s and VTs say it is better than the G20s but definitely there
The owner Happy Nightmares reporting it in the thread above was one of the first ones to own the VT25 in the forum.
Ideally the VT25 has new phosphors and drive electronics which should make it perform better in this area.
But considering the "floating blacks" threads around the net i was expecting them to atleast mention it somewhere in the review, atleast as a comparison with the other panels (even if they did not notice it on the VT25)