No, sunset clauses are not all equal. If it doesn't have a tight "best endeavours" clause - requiring the developer to take all practical steps to achieve registration, for example - then a lawyer would recommend that the clause be amended.
Either the developer would agree to tightening of such clauses, and the buyer would be better protected, or the developer would refuse, and the lawyer would explain to the prospective purchaser precisely what risks they're taking and why it would be a very bad idea.
Would they then have to write what the practical steps are?