One tactic of the CTs I've seen over the years on multiple forums is that when they want to declare something as a fact without evidence to support it, they claim it is "obvious".
As is your custom, you don't quote either Curry or Decker but instead give us your interpretation of what they actually said. Even your interpretation doesn't indicate Curry and Decker deployed their men to the same area. The underpass and the railroad yard are not the same place. Curry and Decker had nothing but sound to base their judgement of the where the shots came from and sound is a poor indicator of that, so yes Curry and Decker were guessing. They were educated guesses based on their impression of where they thought the sounds came from, but they were still guesses. None of their men found any indication of a shooter in either location.
Mr. Griffith is a hopeless cause. He simply makes things up, is caught doing so, then repeats the original claim in a different manner. He doesn't link to primary sources; he takes sources and then re-interprets what he thinks they say. It's endless. His entire conspiracy explanation is a mish mash of contradictory evidence and claims, of sources who are odds with one another, with evidence that actually counters his conspiracy theory.
Curry specifically testified that
he didn't know where the reports/shots came from.
Mr. CURRY - I didn't do that, sir. That was one of my inspectors, I believe that gave that order. I was riding in the Presidential parade and approximately a hundred feet, I guess, ahead of the President's car, and when we heard this first report,
I couldn't tell exactly where it was coming from.Representative FORD - What report are you talking about now?
Mr. CURRY - A sharp report as a firecracker or as it was it was the report of this rifle.
We were just approaching an underpass, and there were some people around on each side of the underpass, up in the railroad yards, and I thought at first that perhaps this was a railroad torpedo, it was a sharp crack.
Mr. CURRY - I said what was that, was that a firecracker, or someone said this, I don't recall whether it was me or someone else, and
from the report I couldn't tell whether it was coming from the railroad yard or whether it was coming from behind but I said over the radio, I said, "Get someone up in the railroad yard and check."
And then about this time, I believe it was motorcycle Officer Chaney rode up beside of me and looking back in the rear view mirror I could see some commotion in the President's car and after this there had been two more reports, but these other two reports I could tell were coming behind instead of from the railroad yards.
Mr. RANKIN - What do you mean by reports?
Mr. CURRY - Sharp reports as a rifle or a firecracker, and looking in the rear view mirror then I could see some commotion in President Kennedy's car.
Mr. RANKIN - You could distinctly hear and tell that the two later reports were from behind?
Mr. CURRY - Behind.
Mr. RANKIN - Rather than front?
Mr. CURRY - That is right.
Mr. RANKIN - You weren't sure whether the first one was from behind or in front?
Mr. CURRY - I couldn't tell because perhaps of the echo or the----
Curry's full testimony is here:
https://www.jfk-assassination.net/russ/testimony/curry1.htm