Where/when did he say that? Certainly not in his WC session.
Plus, there's a need for some more time to pass in order for BRW to join J&N on the 5th floor.....just as James Jarman told the WC here (which is a further indication that Jarman's "12:25 to 12:28" estimate for when they got on the elevator to go up to the fifth floor was not entirely accurate):
Mr. BALL - Did somebody join you then?
Mr. JARMAN - Yes, sir; a few minutes later.
Mr. BALL - Who joined you?
Mr. JARMAN - Bonnie Ray Williams.
Here is what Jarman said....
Mr. JARMAN - This way.
Representative FORD - You went by the front to the corner of Houston and Elm, and then down Houston towards the loading dock?
Mr. JARMAN - Yes, sir.
Representative FORD - And where did you get on the elevator?
Mr. JARMAN - We walked around to the back entrance and went through this door here, and this elevator here was up on six, I believe. And we walked around the elevator and took the west elevator up.
Representative FORD - How could you tell this elevator was at six?
Mr. JARMAN - Because after we got around to the other side we looked up.
Representative FORD - You could see it was on six?
Mr. JARMAN - Yes.
Representative FORD - This was about what time?
Mr. JARMAN -
That was about 12:25 or 12:28. Representative FORD - You got off the fifth floor?
Mr. JARMAN - Yes, sir.
Representative FORD - As you rode the elevator, you noticed the other one was on the sixth floor?
Mr. JARMAN - Right, sir.
Note that when he arrived at the east elevator closest to the back door it was not visible from that position. It was confirmed it was on the sixth floor after they arrived at the west elevator and looked up. He estimates the time was 12.25-12.28, just minutes before the shots. After reaching the SE corner they opened the windows, at that time Williams could have been aware of their presence. Whether that was the reason for him vacating the SN or something else happened after they were there is an interesting question. What would make Williams leave his chicken unfinished and exit the SN to join them just before the motorcade arrived?