I don't see what the noble will get out of finding out the MC'S skill set.
It’s probably just pure curiosity. Recall end of previous chapter where he hand waved the suggestion that Miyabi might be a spy. Duke just really wants to know how Miyabi does the miraculous stuff he does
I also think they might not be actively malicious in trying to scam him into revealing his secrets.
I think they are simply trying to exploit him and I doubt they are going to become antagonists in the end.
Knowledge is also a type of power after all...
The fact somebody as powerful as MC just showed up out of nowhere is a cause for concern even if he is not a direct threat.
He clearly is far from subtle so being a spy is not the case as mentioned before.
He is basically screaming "I am hecking weird " with everything he does.
And knowing more about someone is always better for you than knowing less if you plan to work with somebody.
What I am looking forward to is how the author is going to spin this however...
With how everything has been going so far I assume MC goes along with it.
And the result ends up being an odd situation for everyone because his results do not work/show anything.
Or it just turns out weird in general for extra comedic effect etc.
Not entirely impossible it's just normal but It would be quite the tone shift if it became a super serious situation at least