Not a Finescale Dace
Not a Darter or any of the PA fish listed on the second site you named
You might be correct that it's a minnow species in spawning colors that's not normally seen.
Now, if you made the back a mite lighter, added some green below the darker black, threw in a little spotting and reduced the scarlett to a pinker color, it might be a trout??? Fish & Game put fingerlings and small stockers in the area somewhat below where this fish was caught. Maybe it's a hybrid of some sort!