I have not heard of that before but it actually does not surprise me. I have one theory why a casino might try this...

Might sound a little far fetched at first, but I've read where some people have built home crap tables (or 1/2 tables) so that they can practice throwing. They hold the dice the exact same way for every throw and try to toss them so as not to revolve or spin very much. They also strive to toss them so that they lightly bounce off the back wall as required by the casinos.

They practice for hours and hours and chart all of their throws. They claim because of their skill in throwing the dice, they can statistically show that with practice you can skew the percentages for how many times a seven appears.

I guess if you practice anything enough (trick pool shots, golf shots, whatever) it would sound reasonable that a few would be able to master this.

I have no idea how scared the casinos are of such a player but the players claim that some casinos now harass them if they arrange the dice in a certain way and start winning.

Very similar to the situation between Casinos and blackjack card counters. Some casinos have implemented machines that constantly shuffle the decks and have gone away from dealing from a fixed shoe.