Rod flash as a concern is hooey for all but those who need excuses for a lack of success.
FWIW - I fish the Letort a LOT...
The rod I used most in the olden days is a shiny varnished Leonard 8'0" 6wt 50 M with a peach colored fly line and a shiny mono leader while wearing a white hat and a light sage colored shirt ...
In later years the rod I used the most is a shiny 8'6" 5wt Winston DL4 with a white Rio Lumilux fly line that even GLOWS in the dark with similar clothing and leader...
...the zillions of fish I've landed in all of these trips responded by not giving a rat's a$$...
Before me, much more experienced anglers like Vince Marinaro, Ed Shenk, Charlie Fox & Ernest Schwiebert fished there using shiny varnished Dickinson's, Payne's, Leonard's, Young's; many with shiny nickle silver ferrules and even a hand made 5' creation made by Ed on a shiny Lamiglass blank.
...the fish responded in their lifetimes by not giving a rat's a$$ and providing the material for several books. new fly patterns and new shiny rods built just for that creek...
Meanwhile on the same Letort, some technical schmuck in camo crawling on his belly with dull a 9'0" 2wt rod can't catch squat. Recounting his failures to his buddies, he blames his ineptitude on a twinkle of light from the nippers he had on his subdued zinger...
It beats me, but other than Everett Garrison in the bamboo world who dulled the finish of his rods, nobody else who builds quality rods bothers so there must be a reason.
Maybe those that blame their tackle for their failures should look in the mirror instead of their gear...
...unless they are afraid the mirror is too shiny as well.