I concur. It depends on how tactical the sub is behaving at the time. If it is trying to stay hidden from other submarines or opposing forces, it will be most reluctant to ping actively, most likely at low speed for low noise transmission and to enhance listening ability. If it’s eavesdropping for electronic intelligence it would be at periscope depth an so needs to be very aware of shipping, fishing fleets etc. Drifting fishing nets can catch submarines. Other tactical situations determine what noise/electronic emissions the sub might make.
A bump like this suggests some sort of speed either from the sub itself or the thing that hit it. WE may never know.
A friend of mine was an engineer aboard a British nuclear boat doing a high speed dash across the Atlantic at about 30 knots. The sub struck the top of a hitherto uncharted peak of the Mid-Atlantic Ridge at full speed and fortunately bounced up and over. That’s more than spooky.