Excellent work, Dantenoc. Just for sake of discussion, the lines of position (LOP) not substantiated by celestial observation are known as dead reckoning positions (DR).
You have "nailed" the explanation.
For those who wonder about leaving the Uboat's track to chase target(s)...your other explanations of "How to sink a ship" are just as valid, only now, a lot more challenging. Tnx.