Redband have orange slashes sometimes as well. I don't understand the lineage super well but basically redband are a result of coastal rainbows invading inland cutthroat with varying degrees of success. As an example, the fish in the deschutes river are genetically different than the fish above the falls on the white river due to rainbows having access to the deschutes post-rainbow divergence as a species but not being able to go up the falls on the white river. Interestingly, white river redband above the falls are more genetically similar to Klamath and fort rock redband than deschutes redband. Redband sometimes retain classic inland cutthroat characteristics such as the slash as you've noticed, or a maxillary that extends beyond the eye, or spotting that is heavier towards the posterior of the fish among other things