I would really wonder about John if this meta would prove true.
Like, he faces death and yet he thinks of such trivialities in his very last moments? It´s like standing before a firing squad and to think in your last minute that a Tartar Steak you had at dinner was no fresh or that dress you wore at last ball was out of date. Seriously, who does that? Why would John be worried about the means of Sherlock survival or the details of a "Skeleton Case" in his last seconds on Earth? Wouldn´t the threat of imminent death make those things absolutely insignificant?
Also, he would greatly disappoint me. Because this theory would make his forgiveness (and thus his magnanimous, kind nature) into naught and would replace it with "he held his grudge even beyond grave" revelation. Not sure I would like that.
That aside, I still think that "imagined scene" took place in reality somehow. Anderson is too cosy to Sherlock during a drug bust in HLV. And yet I doubt they are close friends or that they meet frequently. So why is Anderson so bold suddenly? Because that touchy-feely-weepy scene in which he asked for Sherlock´s forgiveness actually happened in Sherlockverse and was not merely a figment of John´s imagination, IMHO.
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I cannot live without brainwork. What else is there to live for? Stand at the window there. Was there ever such a dreary, dismal, unprofitable world? See how the yellow fog swirls down the street and drifts across the dun-coloured houses. What could be more hopelessly prosaic and material? What is the use of having powers, Doctor, when one has no field upon which to exert them?