If it was the truth he would have kept repeating it and the other employees would have stated it was true.
So you accept that Mr Oswald did indeed tell Captain Fritz in that first interrogation session that he visited the second floor lunchroom before the motorcade, then went down to one to eat lunch, then "went outside to watch P. Parade". Excellent: this also commits you to accepting that his bombshell claim---------the single most important thing he said in that session----------was deep-sixed by your 'investigator' heroes whose every word you trust.
Let us now formally add Agent Hosty's same-day account to the top of the interrogation report excerpts you posted!
Instead he changes his story to finally being on the upper floors working during the assassination and only coming down to see what was causing the "commotion".
Why on earth would he do something so mad? All he'd need do-------on your LNer scenario--------is say he was in the second floor lunchroom or the first floor domino room the whole time. There are no conceivable circumstances under which he would tell Captain Fritz, 'Ok ok, I was on one of the upper floors when the President passed the building'. A ludicrous suggestion!
A marine who doesn't know what the sound of gunfire sounds like. His ever changing story places him all over the inside of the building but never in verifiable company of anyone else. The coke on the second floor and the encounter with Baker and Trully is LHO's only constant.
A pity it's not Officer Baker's constant...
Besides, as already pointed out, your argument here is dreadfully weak and selective. Inspector Holmes, upon whose account you're relying 100%, is quite clear on where Mr Oswald places the encounter with Mr Truly and a cop: "First floor. Front entrance to the first floor". Which is where DPD themselves were telling the press 11/22 the encounter happened------and where Mr Lovelady told Mr Jarman he saw the encounter happen.
An encounter that was the result of him coming down the stairs to see what the commotion was all about.
It depends on what 'leaving the building' means. Mr Oswald could have been referring to going down the front steps and out into the street. This is exactly what several people on those steps did.