well I think the decision is to continue following the TR plan, or not.
One key principle in training is specificity. Given your A race is in the future, perhaps TR has you doing longer threshold efforts close to the A race.
“Fractional utilization” or threshold as % FTP is an established concept but somewhat of a distraction. However If you are curious, and have a recent strong 5-min effort and a longer 30-50 minute threshold effort, do this math: Power@5-min / Power@FTP . Do you have good data? If yes, what is it? Again this is a distraction from your main point, and as far as I know TrainerRoad doesn’t consider it when creating plans.