I mean, intentional design can also be a design flaw, so…sure?
Is not being able to tighten a nut a design flaw of a hammer?
The past weekend, I went on a quick trip to Nevada (to see a ballet, of all things), and had to rent a car while I was there. For reasons of availability, they swapped out the compact I had requested to an SUV. This thing was a boat, had issues fitting in some parking spaces, and guzzled gas like there was no tomorrow. I needed a thing for taking my wife and I from point A to Point B on some highways, and a bit of urban driving for sightseeing. What I got was not great for those things.
But not meeting my particular needs didn't mean the SUV was flawed, in and of itself. It would have been fine if I needed to move a crowd of people in notable comfort. It would have been fine if I'd needed to move significant cargo. The design was fine for those tasks - they just weren't
my tasks.
"I got the wrong tool for the job," is not a flaw on the part of the tool.
Mostly, if it’s gonna be possible to be an explorer that can talk to spirits, let Fears No Haints give training in one magic skill. It’s just not doing that narrowness you refer to very well, going partway to allowing niche-combining, but doing so awkwardly.
But allowing niche-combining would mean it wouldn't present the desired genre well - in the original fiction (at least, what I've listened to - I'm not fully caught up), they don't combine niches much. Specifically, characters don't usually have small bits of magic - they are either largely focused on it, or have none.
So, your desired goal of niche-combining seems at odds with the design goal of a game that represents their particular fiction. That's not really a flaw, merely a choice of goals.
Also that text that you quoted was about features having built in specific drawbacks, not about the narrow niche protection of the game.
I didn't quote you any text in this thread. You seem to be confusing me with someone else.