It seems I am mixing up my own VP future ideas with the current rules. Multitask-fail I apologize, consider ‘No enemy subs on your convoy line’ a sneak peek for the future house rules. And mental note not to answer rule questions after a birthday drink.
In V3 it is a bonus indeed. So the wording still needs to be changed by Mr Nice. A sub (raiding or attacking or moving) along a line would be a threat. If it did not raid that turn, does not mean that UK earns that bonus. Why would UK get the bonus if the sub might have just killed 1 destroyer and 4 transports with a bit of dice luck instead of raiding the same sea zone by DOW. Would UK earn that bonus even if the line was packed with 17 subs and no UK fleet to be found within 8 sea zones, because they sank it? The quick and easy fix gives me no satisfaction, but it is what it is. There is an errata for what it is worth. And I have given away an idea I am working on.
Power to the community!