yes, that's true, never question luck
I also noticed that planes are now a big threat; I got (minor) damage 3 times; the first one at the surface (maybe friendly fire? I was in Philippine waters in very early Dec, well before the Japanese invasion started, so I decided not to dive... big mistake). The other 2 times obviously while trying to dive as fast as I can.
Another comment; with TMO you consume fuel while at 0 knots.. which eliminates the exploit of parking your sub at the patrol area for 96 hours