And he's got that lipless grin so common in high pressure C&R waters. The red streak is indeed especially prominent on this 'bow. Neat pic.

I've caught a few in Big Spring that had that mark too over the years.

There has been so much interbreeding between wild rainbows and wild cutthroats that the resulting offspring cutbows have lost any true genetic link generations ago. There is likely a very diluted strain of cutbows in many hatcheries across the US now. Now you have cutbows breeding in the wild with wild rainbows and obviously wherever fish are still stocked they is even more inter species breeding going on. In Montana, where I normally fish, it is indeed very rare to catch a rainbow that doesn't have at least a remnant of the typical under the jaw coloration. There are very few stocked rainbows that don't have a slight orange slash on the underside of the gill cover.

No info, pure conjecture....since cutties are known to be easier to catch than bows, the breeding of hybrids may be intentional to make the fish more angler friendly.