Originally, I had the following sentence:
A Japanese native corrected to be:
I just want to understand what the difference between the 2 words is, and why 本物 is more appropriate in this sentence.
In this context, the doll (or puppet?) is an imitation of real human, so 本物 is felt somewhat more suitable, but it doesn't mean 本当 is invalid or unacceptable here. Besides, the most ideal wording I think would be:
A dictionary says interestingly that 本物 means 本当のもの(こと) and 本当 means 本物のもの(こと), that is to say, they have the same meaning of "real".
However 本当 has some meaning like "true", and 本当 may be used more as the meaning of "true" than "real", so Japanese native might correct 本当 as 本物. I also think 本物 is more common as the meaning of "real" than 本当.
In your sentence 本当の人 does not make any sense. Common use with 本当 is:
When people talk about 本物, they are usually comparing the fake/ similar vs the real one. For ex: