Let’s look at the English language. If I say that “On Sunday, before making the bread, I had to decide to add less salt and more sugar. Nowhere in the sentence does it waffle.
The day is Sunday
the action is making the bread
the subaction is changing the recipe
There is nothing in that sentence that would imply that the bread didn’t get made. The way that bread was made might be changed or maybe not but that bread was made. Period!
The word making or make is clear:
“to cause to happen to or be experienced by someone”
in this case it is clearly “to cause to happen”
You would like for the sentence to say:
“On the character's action, before (choosing, or, deciding to) making(e) attack rolls for a round, the character may choose to subtract a number from all melee attack rolls and add the same number to all melee damage rolls.”
Making is not conditional. It is definitive.
Nothing in the rest of the feat would change “making” to a conditional statement.
If you think it is otherwise show me a sentence that follows your example.