Because at the beginning of the year, you have to be extra careful and take more cautious trades to not step outside your 2% loss limit, but at the end of the year, assuming you are successful, you can afford e.g. 5% loss limit, as you have already made 10% in profit, so you are able to engage in more risky trades.
As this policy were made public at some point, and you usually don't disclose your working risk management profile to the outside world (as it can and will be analyzed and exploited), I can assume that BlueCrest now uses a different approach internally.
As this policy were made public at some point, and you usually don't disclose your working risk management profile to the outside world (as it can and will be analyzed and exploited), I can assume that BlueCrest now uses a different approach internally.