This is the crux of the issue IMO. I feel as a guide/captain I need to set an example of the right way to do things, not just the way that I myself can do things. I can land src with a 4 wt faster than most seem to land them with a 6. However, I don't do this, not do I allow people on my boat to target them with a 4 wt because IME most people lack the fish fighting experience to land any fish quickly, even with the right tool. That isn't a jab at anyone, it's just reality. Most anglers of any sort simply don't catch a ton of fish.
I do not doubt an experienced angler can quickly land a quality steelhead with a trout spey, but those types of anglers are far out numbered by people with far less experience. People hire a guide much of the time because they want to learn how to catch fish. If people see me targeting src with a 4 wt and landing them quickly, then they may go out and buy a 4 themselves and then spend 12 minutes landing 15" fish. It's not a good example for me to be giving. I have to imagine a large portion of Dan's viewer base is newer fly anglers searching the web to learn about all things fly fishing in the NW. If watching a video of him fishing a trout spey for steelhead gives them the impression that this is totally normal and anyone can/should do it, then that's not a good thing IMO.
I do not doubt Dan's ability to quickly land a steelhead using such a rod. No doubt it can be done by those who have the ability and experience to do so. But the simple fact is that most do not. I think anyone in such a position, myself included as a guide, should always be thinking about how our actions are perceived by those with less experience. I catch myself constantly on albacore trips doing things that Id definitely not want my average customer to do. Because I have caught thousands of albacore, I do things that I don't want people who come out once a year to be doing. It's nothing against them or their ability, rather it's a result of the stupid amount of experience I have been blessed to rack up courtesy of my job. But I have to remember that if people see the captain do it, they're likely to think they can do it to.
I'm sure Dan and plenty of others can land a fish quickly on that rod. I'm also just as sure that a high percentage of people watching his videos cannot, and absolutely should not attempt it, and it should not be encouraged or sold by someone in such a position.
Just my take.