You've made some very good points but still there are problems, in my estimate, to be had with speculating on historic events. What I am meaning is that "facts" are not always true. What is stated as a fact in ones testimony, as in the UK news article, does not in and of itself make a fact "true" to a particular historic event. That the NKVD would have liked to have seen Patton dead, or at least some of its agents would have, may itself be a fact...but it is a leap to jump to an NKVD assassination of Patton. Stuff happens. Accidents do happen. People do die. People are killed, murdered or assassinated. Where is the proof, which is especially convenient about 65 years after the event?
A good case in point is speculation about the death of the Princess of Wales. She died. We all have good reason to believe she is dead. I believe she died in a stupid high speed accident like anyone else may have died with a drunk at the wheel hitting an abutment in a tunnel. What a leap it is to speculate that Queen Elizabeth, or other members of the royal family had her killed. People die every day in auto "accidents" who aren't royals. She was mortal like all of us, she got killed, just as we might under similar circumstances. That is what my meaning is/was in saying such speculating stated as facts, are a waste of time, and even dangerous.
That ones interpretation of an event, stated as a fact, happens very often not to be the real "truth" of a matter. For example, witnesses to an accident or a crime very frequently "see" the same event but report different "facts" to investigators. Even in a video (such as the Rodney King beating in Los Angles) many witness reported different "facts" than did other witnesses. Many actual witnesses and later viewers of the video did, or didn't see, what others said were the "facts" in the case. (What I saw in the King beating was six or eight cops taking turns beating King, rather than all of them nailing him to the ground and cuffing him).
These are not dissimilar to what I term as "speculating" on historical events, with flimsy facts and postulating those "facts" as what really did happen. BTW, like you I want to know the "truth" to historic events regardless of who won or lost, but also I don't want to accept as true something that happened long ago and far away based on what some celebrated man alone says happened. One man's truth, could be another man's lie. I don't mind being made aware of a different perspective on an event but I'm not willing to accept that it is a fact in the sense of a historic factual truth.