If true, my guess: little need for the feature, and an understandable reluctance to make the fuze any more complicated than necessary, especially as failures or inadequacies in various sorts of fuze or triggering device have repeatedly caused serious problems with naval ordnance. See: early-war American WWII torpedos basically just not working, British AP shells in the WWI Battle of Jutland detonating too early and so being far less effective than they should have been.
That is odd. I know that during the war in the Pacific the Japanese were extremely careful to avoid having the vastly superior longlance torpedoes fall into the hands of the Allies. They would go to great lengths to search for and recover lost, unexploded torpedos that were in shallow water. It seems like a command-detonation options would be very useful in this regard.
Well, I can guess at a few reasons. 1. As mentioned elsewhere, the radio signal path loss through salt water is astoundingly high -- I did the math once. 2. WW II era radio technology was bulky, and did not work well on batteries -- vacuum tube filaments eat a lot of power and the plate supply requires a high voltage battery. 3. WW II era radio technology did not have encryption built-in -- it would have been pretty easy for the enemy to signal the torpedo to blow up before you launched it, which would kind of ruin your afternoon.
If we follow the spirit of the article, submarine operation is all about stealth. Detonating a (missed) torpedo would give away that there is an engagement, whereas letting it sink is quiet.
I think it just means it's unnecessary. Just disarm the warhead (or inert it) and shut off the torpedo like they describe in the article. The donating part is pointless.
Wireless Signals don't pass through water very well. A submarine has to surface to send messages.
My guess is that any wireless signal would be unlikely to reach a torpedo in motion.
For the torpedos with wires, the article says they can be shut down from afar. Maybe you don't want to blow something up that's close enough to be attached to you via wire. Safer to let it sink.
Why is this so? The wire controls seem sufficient.