WaterMeths is onto it!
For a normal approach with a DH down to 200', the approach climb gradient required is 2.1% for a twin and 2.7% for a quad - JAR 25.121 Subpart B/FAR25.121 Subpart B refer.
However, for instrument approaches with a DH below 200', a OEI gradient of 2.5% is mandated. JAR 1.510 Subpart B and AWO 236 refer.
Thus, a different MAP may be required for Cat 2 and better so we use the cat 2 plate to brief from.
Cheers,
mcdhu