If someone was introduced to a steamboat and they’d never seen a boat before (perhaps a far fetched example but stick with me here), and they made a rowboat and they said that they had built it on steamboat technology (because of the boat part) I think that would not be entirely unreasonable.
A charlatan on the other hand would be someone that sold you a steamboat and then gave you something that was not a steamboat, like for example a big rock or something.
A charlatan decieves people for fame or for money. Someone that sells something as “blockchain” when it’s not is a charlatan. Someone that was inspired to build something by blockchain and describes it as using “blockchain technology” should not deserve to be called a charlatan IMO.
It is still fair to point out that they are not actually using a blockchain, but calling them a charlatan is disingenuous because then what kinds of words should we use to describe the actual charlatans?