I do not have a problem with allowing the person to cancel, especially if they are cancelling a loosing trade. Since the swap provider does not have a similar cancellation ability, I think there should be a cancellation fee for the unused remaining time. That way, the swap taker will be more careful about how many days they take.
+1 I do not understand why any lender would provide more than 2 days given they are giving away free options to borrowers who can refinance without any advantage. There was one before as some borrowers were too lazy to do the smart refinancing themselves, but this new bot would do it for them, so lenders have NO reason to provide more than 2 days anymore.