If I saw a fish rise I'd cast to it.
If I saw a fish behind a rock I'd cast to it.
If I saw V's I'd cast ahead of it.
BUT, I wouldn't wait around for it to happen.
Some people sight fish and ya, it's kinda of annoying at times but the areas they do this are standard.
PS. I've only ever observed the KW and Canal and that's enough for me.
There's to much river to fish without dwelling on the foregone.
Fenceposters:
some fenceposters do it 'cuz they've had luck there (the spot) before, It regularily produces for them.
others fish there with a salmon mentality; the fish will come.
and still others fish there 'cuz well, others are there.
The unintentional fenceposters are eager and bought a rod and reel they haven't yet mastered (cleaning up birdnests).
brought too much gear and have to try everything before they move on.
Try to fish every inch of the grid before they move down stream.
These unintentional fenceposters look like actual fenceposters due to thier intense effort at doing things properly.
Experienced fishers will cover a run in less than half the time a newbie will.
A fencepost isn't always doing it on purpose.
If you see someone struggling give them a bit of guidance, They'll be faster next year
PS KW and canal FF only, but that comes in a month or so anyways.