[trgfdffd]

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.