Yeah, I’d agree. I’ve only used Tiagra, Sora on rental bikes, but they’ve been pretty good. They’re a bit mushier than Dura-Ace. You don’t get that crisp, sharp snap while shifting. And I’d assume they don’t hold up as well to heavy use, but I wouldn’t know for sure.
I wouldn’t be at all surprised if they stand up to heavy use just as well. I believe the priority for the upper tier groups is on weight reduction and stiffness/accuracy rather than wear resistance. This is also where the trickle down may not be complete. While most features trickle down, materials used don’t and complex machining probably doesn’t in most cases. So while functionality trickles down and is by far the most important IMO, weight improvements do not, or at least not to the same extent.