Fair comment.
From the document: (From PD7974 part 0)
This conclusion is equally applicable to building design and BS 7974:2001 has been developed to provide an
objectives-based approach to fire safety in buildings.
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BS 7974:2001 provides a performance-based approach to design in which the specific fire hazards and their
potential consequences are identified and fire safety measures can be introduced, as necessary, to ensure
that the design objectives are met. It also enables the results of recent research into fire and human
response to be translated directly into the building design process.
The QDR process stated in BS7974 sets the performance requirements, so while minimal actual performance criteria is in the codes, (Certain criteria such as suitable limits for tenability are included though) it does point the designer towards setting their own.
This criteria will often be linked to the functional requirements of the building regs. If they go for a comparative study then I don't think they are truly looking at performance, but if they go for the ASET vs RSET thing properly then that is heading more towards performance. i.e. It takes people 15 minutes to evacuate, and we can maintain tenable conditions for 30 minutes. The 'performance' required is the safe evacuation of the building, thus complying with part B1.