The regs say that if an unrestricted tag sells out before August 1st, then the following year it becomes restricted. B zone always sells out, but it doesn't always happen before that August 1st deadline, so most years it remains unrestricted.
Now this year its restricted, so that means that everyone who normally just buys two B zone tags OTC has to wait until after August 1st in order to buy that second tag. It's highly likely that it won't sell out before August 1st this year since the majority of people who buy B zone tags are now limited to just one tag.
I don't think I've ever seen B zone tags sell out before the August 1st deadline more than one year in a row. This means that next year it's likely to go back to being an unrestricted tag.
Like Yoteassasin said the tag quota/allocation hasn't changed.