It doesn't help that all the evidence for who was on the 6th floor just before, during and after the assassination points away from Oswald:
There are four eye-witnesses [Arnold, Roberts, Fischer and Brennan] that got a good look at the man on the 6th floor. Their descriptions of this man are consistent enough for us to conclude they are talking about the same man.
All four eye-witnesses state the man on the 6th floor wore a white/off-white shirt. Three describe it as an open-necked shirt. - a garment Oswald was not wearing that day and did not own.
Another eye-witness, Amos Euins, states time and time again the assassin had a "bald spot" on his head. Not a receding hairline, a bald spot, which is something entirely different:
"I seen a bald spot on this man's head, trying to look out the window. He had a bald spot on his head. I was looking at the bald spot."
Oswald had no such bald spot.
According to the LNer narrative, Oswald hid for over 20 minutes in the SN while BRW had his lunch on the 6th floor. However, Arnold Rowland saw a man with a scoped rifle on the 6th floor SW corner window 15 minutes before the motorcade arrived, at a time when Oswald was supposed to be hiding out in the SN. Arnold also saw a black male in the SN window at a time when BRW was on the 6th floor eating his lunch. Eight officers testified to seeing his lunch remains at the SN, three of the first officers on the scene actually testified that the lunch remains were on top of the boxes that formed the SN.
According to the LNer narrative Oswald rushes from the SN, in order to escape the TSBD. But Howard Brennan describes the assassin lingering at the window, admiring his handiwork. This is from Eyewitness to History:
"My first instinct was to look back up to that man on the sixth floor... By now the motorcade was beginning to speed up and in only a couple of seconds the President's car had disappeared under the triple underpass. To my amazement the man still stood there in the window! He didn't appear to be rushed. There was no particular emotion visible on his face except for a slight smirk. It was a look of satisfaction, as if he had accomplished what he had set out to do."
Harold Norman, directly below the SN hears the bolt of the rifle being worked, he hears the shells hitting the floor, but doesn't hear anyone rushing away from the scene. Jack Dougherty, stood near the stairs on the 5th floor, doesn't hear Oswald as he walks the 20ft across the floor from one staircase to another. Dorothy Garner, who is stood by the stairs, hears Adams and Styles clattering down the stairs. She sees Truly and Baker come up the stairs. But doesn't see or hear Oswald in between the two as he walks the 20ft from one staircase to another. Neither do Betty Ann Foster or Mary Hollies who are stood by the east windows in the storage area of the 4th floor.
Oswald, rushing down through the building, wearing his work shoes on a wooden floor, doesn't make a sound [apparently].
It is reported Oswald stated that Oswald saw James Jarman and Harold Norman on the first floor, making their way to the west elevator after entering the rear door of the TSBD building. This is around 12:25pm, ten minutes after Rowland has spotted the man with the rifle on the 6th floor.
Brennan describes the man he sees on the 6th floor as being much older than Oswald.
He also describes the man as having a "fair complexion".
Ronald Fischer makes a similar observation concerning the man on the 6th floor, but contrasts it with Oswald's "dark" complexion.
"...looking at him from the street in the School Book Depository Building--if I could have been able to---if I could have seen that. I think, if he had been unshaven in the window, it would have made his complexion appear--well---rather dark; but I remember his complexion was light;"
Brennan also describes the shooter as being "neat" - not a word readily associated with Oswald.
It isn't just a case of not having evidence to place Oswald on the 6th floor at the time of the assassination [which Lners don't have], it's the case that whatever credible evidence there is - all of it - points away from Oswald being on the 6th floor at that time.
When will the LN community take this inconvenient fact on board?