The biggest flaw in your story is that Oswald somehow must have known that Norman and Jarman were on the 5th floor when the shots are fired. There is not a shred of evidence for that and it's not really a flaw, it's really something you just made up to "support" your narrative.
It's worse than that. How did Perfidious Assassin Mr Oswald know that Messrs Norman and Jarman were the only two men to come up to 5? For all Perfidious Assassin Mr Oswald knew, Messrs e.g. Lovelady and Arce and Dougherty could have come up with them and taken up positions at more westerly windows.
Now the Davidson answer is: Perfidious Assassin Mr Oswald saw Messrs Norman and Jarman leave the sidewalk and turn north on Houston. Therefore he made a reasonable assumption that they came up alone.
Very well. Let's run with this explanation..............
Where now does this leave the Warren Gullibles in their SIMULTANEOUS enthusiastic embrace of the claim that Mr Oswald went from saying he saw Messrs Norman and Jarman "passing through" to saying he actually
ate lunch with them?
I'll tell you where it leaves them-------------------spluttering in confusion and self-contradiction. Because you can't with a straight face claim that Mr Oswald BOTH craftily crafted a way of putting himself at the rear of the first floor ca. 12:26 AND stupidly botched this brilliant scam by adding a claim that he KNEW did not fit with the facts he had so craftily surmised (that Messrs Norman & Jarman did NOT linger on the first floor en route to the fifth).
The only way the Davidson Explanation holds good is if those pushing the Davidson Explanation concede that those present at the interrogations who reported Mr Oswald as saying he ate lunch with Hank & Junior either lied or misunderstood what Mr Oswald actually said. Who wants to go first?
Our thanks to Mr Organ for exposing the shameless heads-I-win-tails-you-lose approach of the Warren Gullibles to the interrogation reports!