Noble Betting Structure

Hey, does anyone know why Noble's blind structure is only half of the level you're currently playing at in one of their tournaments? For instance, if the current level is 300/600, the Big Blind is 300 and the Small Blind is 150. But if you want to raise, you have to use the increment posted for that level, which is 600.

For instance, I was playing in the Sunday freeroll. We were at the 300/600 level and everyone in front of me had called the BB at 300. I wanted to raise 3 times the BB to 900, but the software wouldn't let me. I could raise to the minimum 600 or go up to 1200, 1800, 2400, etc.

Every other site I play on, the blinds and levels are the same amount in No Limit, although I have seen the half-level structure used in Limit games. Anybody know what that's all about? Is that a common NLHE betting structure in brick & mortar casino tourneys?

Gee, I'm sorry, gang. You must have thought I had lost my mind with this post. I got my sites and tournaments confused. It isn't Noble which has the unusual betting structure of stakes & blinds. It's actually Absolute Poker, where I also played a tourney on Sunday evening after our freeroll.

The rest of the question remains intact. Any insight on this particular set-up?