It is my advice that you ask any builder to fully declare in writing any special conditions to your contract before you hand over any hard earned money or fall in love with the style of the home.
In Victoria The Domestic Building Contracts Act 1995, part 146 clearly calls for restrictions on what the builder can put into a contract. Anything that removes your rights should not be agreed to.
Please be very careful as its some of the big boys that are doing this.
Also be very careful of any letters that they try and get you to sign after signing the contract. If it smells fishy, its generally a dead fish!