I would think that with the right blade, that the time required to master the trick would be a few seconds.
It seems to consist of straight forward sawing with the corner transition being basically the same trick as starting a drywall saw. Wow! How does he do that? Must be a genius. Klausz is super, but nothing he does is impossible to learn, He showed the easy way to do things, and people just went "can't do that" because he is so dang fast. Slow it down, do exactly what he says and it usually is easy.
It would seem one might need two saws or more with the angled section fitting the bottom angle since there are two such angles in a set of DTs, though the cleanup would not be that great.
When I saw him do it first he didn't change saws, maybe the unavailability of new blades is holding him back.
Underhill's problem is bad blade temper. For commercial makers that isn't a problem because they use a "soft" stock and harden each tooth, at least that is an option that would suit this tool.
The way we do dovetails today is closer to being a parlor trick in the sense that it is too fancy and precious by half, and I like that. The first time I read about the Klausz trick he was making shipping containers for his furniture. Considering he could nearly do it as fast as he could nail them together, I think that was very practical. It both provides a great box, and it provides some kind of assurance that the guy you are dealing with is actually competent and his hourly rates aren't based on his lack of productivity.
I used to make cases for returns to the US out of dovetailed packages. I never had a problem but stopped doing it when border controls got worse as it isn't an easy package to get into. And goodness knows what it looks like in an X-ray. I liked doing that because while nobody ever turned down a return, you know what they are thinking; "not my fault, the clod broke it". Well send it in a nice box and they probably cut you some slack. Remember being in LV one time, and they were blowing out Iroyoi timber framing/mortise chisels for about 10 bucks. Turned out "every" single one they had sold had been broken, by the happy owners. who apparently though they were buying crowbars at the home center. Imagine you are the one guy who knows how to use that chisel and sends it back... Well I guess it wouldn't mater, but pride dictated returns in a nice box.
So no, it isn't a trick, it is an efficient way to make a joint that has many uses, but people hold back from using it because they take too long to make in some cases. I used housed dovetails in a transition between two materials in my back yard fence. I join panels of plywood to make sturdy boxes for the shop, though I have my own way of doing that with special tooling, but the inspiration was the Klausz/Euro trick.