Ideally, you have a V&V Plan that would define how you verify the requirements are met and validate that user needs are met. Otherwise, when you're asked how you validated the design, you might not have a good answer!
Since you're filing a 510(k), presumably there's a predicate device. As such, there's probably already something of a human factors standard or expectation. If you dramatically change that aspect then you might have a hard time showing that the user needs are met unless you do something like a human factors study.
So the bottom line is that you do need to plan out what you intend to do such that it's defensible. Consider risk to assess the types of validation testing to perform. If there's no risk of misuse or erroneous use due to how you implement the human factors aspect, then maybe a study is warranted.