I propose that it depends on why it's difficult to implement. If the behaviour is easy to explain in English but requires a complex technical solution to enable it then that's one matter.
However, if you struggle to even describe the behaviour in English then it is a good indicator that users may struggle to understand it too.
I am assuming this is the case here. It may be that the OP had a very clear idea of how the gravity and all its edge cases would hang together but just struggled to code it. I interpreted the article's wording differently.
I do think not being able to simply describe a key game mechanic in natural language is indicative that it may be hard for users to deduce too.
However, if you struggle to even describe the behaviour in English then it is a good indicator that users may struggle to understand it too.
I am assuming this is the case here. It may be that the OP had a very clear idea of how the gravity and all its edge cases would hang together but just struggled to code it. I interpreted the article's wording differently.
I do think not being able to simply describe a key game mechanic in natural language is indicative that it may be hard for users to deduce too.