The performance data in the Airplane Flight Manual applies in determining compliance with §§121.175 through 121.197 ...
To my simple mind it follows that, if you are required to follow the operations documentation .. then you are required to follow the Flight Manual requirements ?
This means that the
performance data was used to determine compliance. Its doesnt say how it was used, or other mitigations on the compliance, it just states that this particular dataset was 'applied in the determination'
The specific FM will be the compilation of all of the negotiations, mitigations, and determinations for compliance of that specific variant.