What rule do I break if I plan to land with 45 minutes FFR then make an in-flight decision to instead land with 30? What rule? I think you’ll find the answer is: No rule.
What is the safety issue if I decide to land with 30 minutes reserve, and I in fact land with 30 minutes reserve? The safety issue.
What if I decided from the start to land with 30 minutes reserve rather than 45, and in fact land with 30? If that’s not a safety issue, why does it become a safety issue if I instead planned to land with 45 minutes reserve then make an in-flight decision to land with 30 as a consequence of higher winds than forcecast, and in fact land with 30?
What is reserve fuel for?