The post you are reporting:
The chances of two submarines being at the same depth in the same place in the middle of the North Atlantic seem vanishingly small, even given the fact that ICBM submarines lurk in suitable underwater canyons which may reduce the odds to millions to one. Obviously employing active sonar would immediately show the location of the other submarine but would reveal the transmitting boats own position and defeat the object of the mission, to remain completely invisible.
The highly sophisticated passive sonar arrays can detect an aircraft carrier proceeding at speed on the surface a couple of hundred miles away but locating another submarine at depth in stealth mode is a different matter. The fact that neither of these appear to have detected one another is a testimony to all the advances in quiet running - gearing, propellers, anechoic tiles, anti-sonar equipment etc - or just possibly they were playing games.
Incidentally, there is no truth in the comment in the Sun that the French submarine surrendered after they felt the impact.
There is bound to have been much more to this than we have been told. The world of the submariner is esoteric and cloaked in secrecy. Throughout the Cold War and beyond, British and American submarines have been engaged in a deadly game of hunt and seek with their Soviet counterparts.
I remember reading an article in the old Nautical Magazine about the Hughes Glomar Explorer when she was constructed several decades ago purportedly to harvest manganese nodules from the seabed at enormous depths. It was a very long time before I discovered that this was only a cover for a clandestine CIA-funded mission to recover a sunken Soviet nuclear submarine from the floor of the Pacific. The Americans knew her position from their seabed underwater listening arrays but the Russians were in the dark. The wreck broke in half on the way up but they still recovered a lot of useful stuff.
Similarly, I was enthralled when Dr Robert Ballard located and photographed the wreck of the Titanic. It was only much later, when the information was declassified, that he revealed that he had been funded by the US Navy but only on condition that he first located and recorded the wrecks of the two USN nuclear submarines which had sunk in the North Atlantic, USS Thresher and USS Scorpion.