On my auto (thought this was for all the trannies?) the TC rear output shaft has a 4-bolt flange on it, just like the pinion flange on the rear differential 3rd member. The draiveshaft has the U-joints afixed to either end of it, these are what attach to the output shaft. So it's nice and easy to take off (well, once it's been off recently, anyway!).

Re: hydraulics engaging park, that's probably correct. However, I don't see ewhy this would matter?
If the tranny is in park, shouldn't that lock the output that goes INTO the TC, hence locking both outputs of the TC?
To me this behavior suggests the units are more integrated than that.