Oh but it matters very much indeed.
Remember: if they know that Mr Oswald was out front for the shooting, then they know that there is every risk that visual proof and/or witnesses may emerge at some point to prove his presence there. This means that the new, fictional location for the encounter has to be somewhere that Mr Oswald could physically and halfway plausibly have gone to from the front entrance immediately after the shooting. Otherwise Officer Baker and Mr Truly (and others besides) risk exposure as rank perjurers. Due to the layout of the building, and of the second floor in particular, the lunchroom is the least worst (actually the only) option
This is daft. So you're basically saying that they were worried about the possibility of visual proof or witnesses emerging which could prove Oswald was out front at the time of the shooting?
Rather than just concern about Baker and Truly being exposed as perjurers, what would it have meant on the grand overall scale of things if such evidence had emerged? Would they have just dismissed the whole Oswald as the shootist theory and said "Oh, well it was plausible that he was in the 2nd floor lunchroom so it at least it means Baker and Truly won't get charged for perjury"?
If they'd gone to all the trouble of setting Oswald up as a patsy then surely making sure that visual evidence or human witnesses claiming he was elsewhere at the exact time of the shooting would have been taken care of?
Again, the fictional encounter HAS to work both ways: an assassin who has descended OR (if it comes to it) a man who has just left the front entrance and come upstairs
But surely there's no significant time difference between someone who has gone upstairs, got a Coke and stood around in the lunchroom before being seen and someone who has gone upstairs, got a Coke and then started to make his way back downstairs again. In both versions the same man is still basically on the 2nd floor just in different locations.
They knew Mr Oswald wasn't the shooter, and their options were excruciatingly limited. The lunchroom was lousy, but it was their only option if they were to keep alive the notion of Mr Oswald's guilt as the sixth-floor shooter
Another thing that doesn't make sense about this theory; what was Truly's role in all this and why would he have been so eager to go along with the story of Oswald being in the 2nd floor lunchroom if it was completely fabricated? What was in it for him?
If he could so easily have been forced to lie then surely anyone claiming they saw Oswald outside could have been made to lie also...or maybe they were?