Couple things - they're surfaced in the straight near Brest not because of the reactor, but because it's too shallow to operate. For example, US East-coast submarines have to transit for hours on the surface to get to the dive point because of the continental shelf. On the US West coast (Hawaii, San Diego), they can pretty much dive shortly after leaving port.

More people than the Commanding Officer and Executive Officer would know their position, though. Whoever is the French equivalent of Officer of the Deck and the on-duty navigator would need to know their position. But yeah, there are times/situations where the position of the boat is MUCH more closely held - and that may be all the time on French ballistic missile submarines.